Protective sheet for solar battery module, method of fabricating the same and solar battery module

ABSTRACT

A protective sheet for a solar battery module comprises a weather-resistant sheet ( 1 ) of, for example, a fluorocarbon resin, and a deposited inorganic oxide thin film ( 2 ) formed on one of the surfaces of the weather-resistant sheet ( 1 ). A surface-treated layer ( 3 ) is formed in the weather-resistant sheet ( 1 ) to enhance adhesion between the weather-resistant sheet ( 1 ) and the deposited inorganic oxide thin film ( 2 ).

This application is a division of Ser. No. 09/418,193 filed Oct. 13,1999 now U.S. Pat. No. 6,335,479.

TECHNICAL FIELD

The present invention relates to a protective sheet for a solar batterymodule, a method of fabricating the protective sheet and a solar batterymodule provided with the protective sheet. More specifically, thepresent invention relates to a protective sheet for protecting the frontsurface or the back surface of a solar battery module, excellent inproperties including strength, weather resistance, heat resistance,light resistance, wind endurance, hailstorm resistance, chemicalresistance, moisture resistance and soil resistance, and having veryhigh durability and protective ability; and solar battery moduleemploying the protective sheet.

BACKGROUND ART

With an increasing rise in awareness of environmental problems, solarbatteries as clean energy sources have attracted a great deal ofattention. Various types of solar battery modules have been developedand proposed in recent years.

Generally, a solar battery module is fabricated, for example, byfabricating silicon solar cells or amorphous silicon solar cells,superposing a protective sheet, a filler layer, a layer provided withsolar cells, i.e., photovoltaic cells, a filler layer and a backprotective sheet in that order in a laminated structure, bringing thosecomponent layers into close contact by vacuum, and laminating thosecomponent layers by a lamination process.

The solar battery modules were applied to pocket calculators in theearly stage of solar battery application and, subsequently, began to beapplied to various kinds of electronic apparatuses. The field of civilapplication of solar battery modules have rapidly been spreading inrecent years. The most important object of the solar battery moduleapplication will be the realization of large-scale, concentrated solarbattery power generation.

The presently most common front surface protective sheet for the solarbattery module is a glass sheet. Resin sheets, such as fluorocarbonresin sheets, have become notable in recent years and the development ofresin sheets is in rapid progress.

Resin sheets excellent in strength are the most commonly used as theback protective sheet for the solar battery module. Metal sheets alsoare used as back protective sheets.

Generally, a protective sheet included in a solar battery module, forexample, a front surface protective sheet, must be highly transparent tosunlight because the solar battery absorbs sunlight for photovoltaicpower generation, and excellent in properties including strength,weather resistance, heat resistance, water resistance, light resistance,wind endurance, hailstorm resistance and chemical resistance.Particularly, the protective sheet must be excellent in moisture-proofproperty to prevent the permeation of moisture and oxygen, have a highsurface hardness, excellent in soil resistance to prevent dustaccumulation, have very high durability and protective ability. The backprotective sheet must meet substantially the same conditions as thosefor the front surface protective sheet.

The glass sheet, which is the most commonly used at present as the frontsurface protective sheet of the solar battery module, has a highsunlight transmittance, is excellent in properties relating todurability, such as weather resistance, heat resistance, waterresistance, light resistance and chemical resistance, is excellent inmoistureproof property, has a high surface hardness, is excellent insoil resistance to prevent dust accumulation and has high protectiveability. However, the glass sheet is inferior in strength, plasticity,impact resistance, workability, handling facility and cost.

Although the fluorocarbon resin sheet serving as the front surfaceprotective sheet of the solar battery module, as compared with the glasssheet, is satisfactory in strength, plasticity, impact resistance andweight, the same is inferior in properties relating to durabilityincluding weather resistance, heat resistance, water resistance lightresistance and chemical resistance, and is particularly unsatisfactoryin moistureproof property and soil resistance.

Although a resin sheet having a high strength, as employed as the backprotective sheet of the solar battery module, is satisfactory instrength, plasticity, impact resistance, weight and cost, the same isinferior in properties relating to durability including weatherresistance, heat resistance, water resistance, light resistance andchemical resistance and, particularly, lacks moistureproof property andsoil resistance.

There have been a proposal to use sheets of a material having anexcellent gas-barrier property and impermeable to moisture, oxygen gasand the like as the front or the back surface protective sheet of thesolar battery module. The most commonly used sheets having an excellentgas-barrier property are aluminum foils.

Although very excellent in gas-barrier property, aluminum foils causeproblems in the disposal thereof and, basically, aluminum foils areopaque and obstruct the view of things behind them.

A resin film excellent in gas-barrier property, such as a film of apolyvinylidene chloride resin, or a polyvinyl alcohol resin or anethylene-vinyl alcohol copolymer is a previously proposed resin filmexcellent in gas-barrier property. The resin film of a polyvinylidenechloride resin produces chlorinated gases when incinerated. Therefore,it is undesirable to use such a film in view of preventing environmentalpollution. Basically, the gas-barrier property of that resin film is notnecessarily satisfactory and that resin film is unsuitable for usesrequiring a high gas-barrier property. The resin film of the polyvinylalcohol resin or the ethylene-vinyl alcohol copolymer has a relativelyexcellent gas-barrier property in an absolute dry condition and is notsatisfactory in impermeability to moisture. The impermeability of thisresin film to oxygen gas deteriorates under a moist condition.Accordingly, this film is unsuitable, from the practical point of view,for use as a gas-barrier film.

A recently proposed gas-barrier film excellent in gas-barrier propertyis, for example, an inorganic oxide film, such as a silicon oxide filmor an aluminum oxide film, deposited by a physical vapor depositionprocess, such as a vacuum evaporation process, or a chemical vapordeposition process, such as a low-temperature plasma chemical vapordeposition process.

The gas-barrier film formed by depositing such an inorganic oxide is anaggregate of inorganic oxide grains and inevitably has defects in itsstructure, which limits reliability in gas-barrier property. Since sucha gas-barrier film has a glassy structure, the gas-barrier film isinferior in flexibility and is subject to cracking when mechanicalstress is induced therein. When cracked, the gas-barrier property of thegas-barrier film deteriorates greatly.

A previously proposed composite gas-barrier film is a multilayergas-barrier film comprising a plurality of component films formed by amultistage vapor deposition process. Another previously proposedcomposite gas-barrier film comprises a resin film having an excellentgas-barrier property and a deposited inorganic oxide film deposited onthe surface of the resin film. These composite gas-barrier films are notnecessarily satisfactory.

DISCLOSURE OF THE INVENTION

The present invention provides a safe protective sheet for a solarbattery module, having a high strength, excellent in propertiesincluding weather resistance, heat resistance, water resistance, lightresistance, wind endurance, hailstorm resistance, chemical resistance,moisture resistance and soil resistance, greatly improved inmoistureproof property to prevent the permeation of moisture and oxygen,capable of limiting long-term deterioration to the least extent, havingvery high durability and protective ability, and capable of beingmanufactured at a low cost; a method of fabricating the protectivesheet; and a solar battery module.

The present invention provides a protective sheet for a solar batterymodule, comprising a weather-resistant sheet and an inorganic oxide thinfilm deposited on one surface of the weather-resistant sheet by vapordeposition.

The present invention provides a protective sheet for a solar batterymodule, formed by superposing a pair of laminated sheet each comprisinga weather-resistant sheet and an inorganic oxide thin film deposited byvapor deposition.

The present invention provides a protective sheet for a solar batterymodule, comprising a weather-resistant sheet and an ultraviolet rayintercepting layer, an infrared ray intercepting layer or a highlyreflecting layer.

The present invention provides a method of fabricating a protectivesheet of a laminated construction comprising at least aweather-resistant sheet and an ultraviolet ray intercepting layer formedon the weather-resistant sheet for a solar battery module, comprisingthe steps of: preparing the weather-resistant sheet; and forming theultraviolet ray intercepting layer by applying a coating resin liquidcontaining TiO₂ or CeO₂ having a mean grain size in the range of 1 to100 nm dispersed therein to the weather-resistant sheet and drying thesame.

The present invention provides a method of fabricating a protectivesheet of a laminated construction comprising at least aweather-resistant sheet and an infrared ray intercepting layer formed onthe weather-resistant sheet for a solar battery module, comprising thesteps of: preparing the weather-resistant sheet; and forming theinfrared ray intercepting layer y depositing a metal on theweather-resistant sheet by vapor deposition or by applying a coatingresin liquid containing a metal oxide particles dispersed therein to theweather-resistant sheet and drying the same.

The present invention provides a solar battery module comprising: solarcells; a pair of filler layers sandwiching the solar cells therebetween;and a pair of protective sheet disposed on the filler layers,respectively; wherein at least one of the protective sheet comprises aweather-resistant sheet and an inorganic oxide thin film formed by vapordeposition.

The present invention provides a solar battery module comprising: solarcells; a pair of filler layers sandwiching the solar cells therebetween;and a pair of protective sheet disposed on the filler layers,respectively; wherein at least one of the protective sheet is formed bysuperposing a pair of laminated structures each comprising aweather-resistant sheet and an inorganic oxide thin film formed by vapordeposition.

The present invention provides a solar battery module comprising: solarcells; a pair of filler layers sandwiching the solar cells therebetween;and a pair of protective sheet disposed on the filler layers,respectively; wherein at least one of the protective sheet comprises aweather-resistant sheet, and an ultraviolet ray intercepting layer, aninfrared ray intercepting layer or a highly reflective layer formed onone of the surfaces of the weather-resistant sheet.

The present invention provides a solar battery module comprising: solarcells; a pair of filler layers sandwiching the solar cells therebetween;and a pair of protective sheet disposed on the filler layers,respectively; wherein at least one of the protective sheet comprises aweather-resistant sheet and a light confining layer formed on one of thesurfaces of the weather-resistant sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a typical sectional view of a protective sheet in a firstembodiment according to the present invention for a solar batterymodule;

FIG. 2 is a typical sectional view of a protective sheet for a solarbattery module;

FIG. 3 is a typical sectional view of a protective sheet for a solarbattery module;

FIG. 4 is a typical sectional view of a protective sheet for a solarbattery module;

FIG. 5 is a typical sectional view of a solar battery module providedwith the protective sheet shown in FIG. 1;

FIG. 6 is a typical sectional view of a solar battery module providedwith the protective sheet shown in FIG. 1;

FIG. 7 is a typical sectional view of a solar battery module providedwith the protective sheet shown in FIG. 1;

FIG. 8 is a diagrammatic view of a continuous vapor deposition systemfor forming an inorganic oxide thin film by physical vapor depositionprocess for vapor deposition

FIG. 9 is a diagrammatic view of a low-temperature plasma chemical vapordeposition system for forming an inorganic oxide thin film by a physicalvapor deposition process for vapor deposition;

FIG. 10 is a typical sectional view of a protective sheet in a thirdembodiment according to the present invention for a solar batterymodule;

FIG. 11 is a typical sectional view of a protective sheet for a solarbattery module;

FIG. 12 is a typical sectional view of a protective sheet for a solarbattery module;

FIG. 13 is a typical sectional view of a solar battery module providedwith the protective sheet shown in FIG. 10;

FIG. 14 is a typical sectional view of a solar battery module providedwith the protective sheet shown in FIG. 10;

FIG. 15 is a typical sectional view of a solar battery module providedwith the protective sheet shown in FIG. 10;

FIG. 16 is a typical sectional view of a protective sheet in a fourthembodiment according to the present invention for a solar batterymodule;

FIG. 17 is a typical sectional view of a protective sheet for a solarbattery module;

FIG. 18 is a typical sectional view of a protective sheet for a solarbattery module;

FIG. 19 is a typical sectional view of a protective sheet for a solarbattery module;

FIG. 20 is a typical sectional view of a protective sheet for a solarbattery module;

FIG. 21 is a typical sectional view of a solar battery module providedwith the protective sheet shown in FIG. 16;

FIG. 22 is a typical sectional view of a solar battery module providedwith the protective sheet shown in FIG. 16;

FIG. 23 is a typical sectional view of a solar battery module providedwith the protective sheet shown in FIG. 16;

FIG. 24 is a typical sectional view of a protective sheet in a fifthembodiment according to the present invention for a solar batterymodule;

FIG. 25 is a typical sectional view of a protective sheet for a solarbattery module;

FIG. 26 is a typical sectional view of a protective sheet for a solarbattery module;

FIG. 27 is a typical sectional view of a protective sheet for a solarbattery module;

FIG. 28 is a typical sectional view of a protective sheet for a solarbattery module;

FIG. 29 is a typical sectional view of a solar battery module providedwith the protective sheet shown in FIG. 24;

FIG. 30 is a typical sectional view of a protective sheet in Example 1in a seventh embodiment according to the present invention for a solarbattery module;

FIG. 31 is a typical sectional view of a protective sheet in Example 2in a seventh embodiment according to the present invention for a solarbattery module;

FIG. 32 is a typical sectional view of a protective sheet in Example 3in a seventh embodiment according to the present invention for a solarbattery module;

FIG. 33 is a typical sectional view of a protective sheet in Example 4in a seventh embodiment according to the present invention for a solarbattery module;

FIG. 34 is a typical sectional view of a solar battery module embodyingthe present invention;

FIGS. 35(a) to 35(e) are typical sectional views of assistance inexplaining a process of fabricating a protective sheet in an eighthembodiment according to the present invention for a solar batterymodule;

FIGS. 36(a) to 36(e) are typical sectional views of assistance inexplaining a process of fabricating a protective sheet in a modificationof the protective sheet shown in FIG. 35;

FIGS. 37(a) and 37(b) are typical sectional views of a light confininglayer included in a protective sheet for a solar battery module;

FIGS. 38(a), 38(b) and 38(c) are a typical plan view, a typicalsectional view and a typical perspective view, respectively, of anexample of a reflecting structure included in the light confining layershown in FIGS. 37(a) and 37(b);

FIGS. 39(a), 39(b) and 39(c) are a typical plan view, a typicalsectional view and a typical perspective view, respectively, of anotherexample of a reflecting structure included in the light confiningstructure; and

FIG. 40 is a typical sectional view of a solar battery module embodyingthe present invention provided with a protective sheet.

REST MODE FOR CARRYING OUT THE INVENTION FIRST EMBODIMENT

The present invention will be described hereinafter with reference tothe accompanying drawings.

In this description, the term “sheet” is used in its broad sense todenote both sheets and films, and the term “film” is used in its broadsense to denote both sheets and films.

FIGS. 1 to 4 are typical sectional views of protective sheets inexamples in a first embodiment according to the present invention for asolar battery module, and FIGS. 5 to 6 are typical sectional views ofsolar battery modules employing the protective sheet shown in FIG. 1.

Referring to FIG. 1, a protective sheet A embodying the presentinvention for a solar battery module comprises a fluorocarbon resinsheet (weather-resistant sheet) 1, and a deposited inorganic oxide thinfilm 2 formed on one of the surfaces of the fluorocarbon resin sheet 1.

As shown in FIG. 2, a protective sheet A, in an example of the firstembodiment for a solar battery module is formed by surface-treating oneof the surfaces of a fluorocarbon resin sheet 1 to form asurface-treated layer 3, and forming a deposited inorganic oxide thinfilm 2 on the surface-treated layer 3 of the fluorocarbon resin sheet 1.

As shown in FIG. 3, a protective sheet A₂ in another example of thefirst embodiment for a solar battery module is formed by forming amultilayer film 4 consisting of at least two deposited inorganic oxidethin films 2 on one of the surfaces of a fluorocarbon resin sheet 1.

As shown in FIG. 4 a protective sheet A₃ in a third example of the firstembodiment for a solar battery module comprises a fluorocarbon resinsheet 1 and a composite film 5 formed on one of the surfaces of thefluorocarbon resin film 1. The composite film 5 consists of a firstdeposited inorganic oxide thin film 2 a formed on one of the surfaces ofthe fluorocarbon resin sheet 1 by a chemical vapor deposition process,and a second deposited inorganic oxide thin film 2 b of an inorganicoxide different from that of the first deposited inorganic oxide film 2a, formed on the first deposited inorganic oxide thin film 2 a by aphysical vapor deposition process.

Those protective sheets are only examples of the protective sheet in thefirst embodiment and the present invention is not limited thereto.

For example, in each of the protective sheets shown in FIGS. 3 and 4,the surface of the fluorocarbon resin sheet 1 may be finished in asurface-treated surface similar to the surface-treated surface 3 shownin FIG. 2. In the protective sheet A₃ shown in FIG. 4, a depositedinorganic oxide thin film may be formed first on the surface of thefluorocarbon resin sheet 1 by a physical vapor deposition process, andthen another deposited inorganic oxide thin film may be formed by achemical vapor deposition process.

A solar battery module employing this protective sheet A embodying thepresent invention and shown in FIG. 1 will be described by way ofexample. Referring to FIG. 5, a solar battery module T employs theprotective sheet A shown in FIG. 1 as its front surface protective sheet11. The solar battery module T is fabricated by superposing theprotective sheet 11(A), a filler layer 12, a photovoltaic layer 13 ofsolar cells, a filler layer 14 and a generally known back surfaceprotective sheet 15 in that order in a superposed structure, andsubjecting the superposed structure to a generally known formingprocess, such as a surlamination process, in which those componentlayers of the superposed structure are brought into close contact byvacuum and are bonded together by hot pressing. The deposited inorganicoxide thin film 2 of the protective sheet 11 faces inside.

Another solar battery module T₁ shown in FIG. 6 employs the protectivesheet A shown in FIG. 1 as its back surface protective sheet 16. Thesolar battery module T₁ is fabricated by superposing a generally knownfront surface protective sheet 17, a filler layer 12, a photovoltaiclayer 13 of solar cells, a filler layer 14 and the protective sheet16(A) in that order in a superposed structure, and subjecting thesuperposed structure to a generally known forming process, such as alamination process, in which those component layers of the superposedstructure are brought into close contact by vacuum and are bondedtogether by hot pressing. The deposited inorganic oxide thin film 2 ofthe protective sheet 16 faces inside.

A third solar battery module T₂ shown in FIG. 7 employs the protectivesheet A shown in FIG. 1 as its front surface protective sheet 11 and itsback surface protective sheet 16. The solar battery module T₂ isfabricated by superposing the front surface protective sheet 11(A), afiller layer 12, a photovoltaic layer 13 of solar cells, a filler layer14 and the protective sheet 16(A) in that order in a superposedstructure, and subjecting the superposed structure to a generally knownforming process, such as a lamination process, in which those componentlayers of the superposed structure are brought into close contact byvacuum and are bonded together by hot pressing. The deposited inorganicoxide thin film 2 of each of the protective sheets 11 and 16 facesinside.

The foregoing protective sheets in accordance with the present inventionand the foregoing solar battery modules employing those protectivesheets are examples intended to illustrate the invention and not to beconstrued to limit the scope of the invention.

For example, the protective sheets shown in FIGS. 2, 3 and 4 can beapplied to solar battery modules of various types. The foregoing solarbattery modules may comprise additional layers for sunlight absorption,reinforcement or the like.

Materials for and methods of fabricating the protective sheets inaccordance with the present invention and the solar battery modulesemploying those protective sheets will be described. The fluorocarbonresin sheet 1 for the protective sheets embodying the present inventionand the solar battery modules employing those protective sheets is atransparent film or a transparent sheet of any one ofpolytetrafluoroethylene (PTFE), perfluoroalcoxy resins (PFA), i.e.,copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ether,tetafluoroethylene-hexafluoropropylene copolymers (FEP),tetrafluoroethylene-perfluoroalkyl vinyl ether-hexafluoropropylenecopolymers (EPE), tetrafluoroethylene-ethylene or propylenecopolymers(ETFE), polychlorotrifluoroethyleneresins (PCTFE),ethylene-chlorotrifluoroethylene copolymers (ECTFE), vinylidene fluorideresins (PVDF), and polyvinyl fluorides (PVF).

Sheets of polyvinyl fluorides (PVF) and tetrafluoroethylene-ethylene or-propylene copolymers (ETFE) among the foregoing fluorocarbon resinsheets 1 are most preferable from the viewpoint of transparency andtransmittance to sunlight.

The protective sheets of the solar battery modules using thefluorocarbon resin sheet 1 utilize the excellent properties of thefluorocarbon resin sheet 1 including mechanical properties, heatresistance, optical properties, weather resistance including lightresistance, heat resistance, water resistance and the like, soilresistance and chemical resistance. The protective sheet is equal inoptical properties and durability to a glass sheet generally used as aprotective sheet, has satisfactory mechanical properties, and is moreflexible and lighter than a glass sheet, excellent in workability andeasy to handle.

The fluorocarbon resin sheet 1 may be, for example, any one of films orsheets of the foregoing fluorocarbon resins formed by a film formingprocess, such as an extrusion process, a casting process, a T-dieextrusion process, a cutting process, an inflation process or the like,any one of multilayer films or multilayer sheets of two or more kinds ofthe foregoing fluorocarbon resins formed by a coextrusion process, orany one of films or sheets formed by subjecting a mixture of a pluralityof kinds of the foregoing fluorocarbon resins to a film forming process.When necessary, the fluorocarbon resin sheet 1 may be a uniaxially orbiaxially oriented film or sheet formed by subjecting a fluorocarbonresin film or sheet to a uniaxial or biaxial orientation process of atenter system or a tubular film system.

The thickness of the fluorocarbon resin sheet is in the range of about12 to about 200 μm, desirably, in the range of about 25 to about 150 μm.

It is desirable that the fluorocarbon resin sheet 11 of the presentinvention has a visible light transmittance of 90% or above, preferably,95% or above and a property to transmit all incident sunlight and toabsorb the same.

When forming the fluorocarbon resin sheet, various compoundingingredients and additives may be added to the fluorocarbon resin toimprove the workability, heat resistance, weather resistance, mechanicalproperties, dimensional stability, oxidation resistance, slipperiness,releasability, flame retardancy, antifungal property, electricproperties and the like. The amount of each of the compoundingingredients and the additives is in the range of a very small percent toseveral tens percent and may optionally be determined according to thepurpose.

The fluorocarbon resin may contain commonly known additives, such as alubricant, a crosslinking agent, an oxidation inhibitor, an ultravioletabsorber, a light stabilizer, a filler, a reinforcing material, astiffener, an antistatic agent, a flame retarder, a flame-resistantagent, a foaming agent, an antifungus agent, a pigment and the like. Thefluorocarbon resin may further contain modifiers.

In the present invention, it is preferable to use a fluorocarbon resinsheet of a fluorocarbon resin produced by preparing a mixture of afluorocarbon resin, and an oxidation inhibitor or an ultravioletabsorber, and kneading the mixture.

In the present invention, it is preferable to use a fluorocarbon resinsheet of a fluorocarbon resin produced by preparing a mixture of afluorocarbon resin, an oxidation inhibitor and/or an ultravioletabsorber, and kneading the mixture.

The ultraviolet absorber absorbs detrimental ultraviolet rays containedin sunlight, converts the energy of ultraviolet rays into harmlessthermal energy in its molecules to prevent active species that startsthe photodeterioration of polymers from being excited. One or some ofultraviolet absorbers, such as those of a benzophenone group, abenzotriazole group, a salicylate group, an acrylonitrile group,metallic complex salts, a hindered amine group and an inorganicultraviolet absorber, such as ultrafine titanium oxide powder (particlesize: 0.01 to 0.06 μm) or ultrafine zinc oxide powder (particle size:0.01 to 0.04 μm), may be used.

The oxidation inhibitor prevents the light deterioration or thermaldeterioration of polymers. Suitable oxidation inhibitors are, forexample, those of a phenol group, an amine group, a sulfur group, aphosphoric acid group and the like.

The ultraviolet absorber or the oxidation inhibitor may be anultraviolet absorbing polymer or an oxidation inhibiting polymerproduced by chemically bonding an ultraviolet absorber of thebenzophenone group or an oxidation inhibitor of the phenol group to theprincipal chains or the side chains of a polymer.

The ultraviolet absorber and/or the oxidation inhibitor content isdependent on the shape and density of particles and a preferableultraviolet absorber and/or the oxidation inhibitor content is in therange of about 0.1 to about 10% by weight.

When necessary, a surface-treated layer 3 may be formed in a surface ofthe fluorocarbon resin sheet 1 by a surface pretreatment process toimprove the adhesion between the surface of the fluorocarbon resin sheet11 and the deposited inorganic oxide thin film 2.

The surface-treated layer 3 may be formed by, for example, a coronadischarge treatment, an ozone treatment, a low-temperature plasmatreatment using oxygen gas or nitrogen gas, a glow discharge treatment,an oxidation treatment using a chemical or the like. The surface-treatedlayer 3 may be a corona-treated layer, an ozone-treated layer, aplasma-treated layer, an oxidized layer or the like.

The surface pretreatment of the fluorocarbon resin sheet may be carriedout before forming the deposited inorganic oxide thin film. When thesurface of the fluorocarbon resin sheet is to be treated by alow-temperature plasma process or a glow discharge process, the surfacepretreatment may be carried out in an in-line processing mode as apretreatment process in a process for forming the deposited inorganicoxide thin film, which is effective in reducing the manufacturing cost.

The surface of the fluorocarbon resin sheet 1 is finished by the surfacepretreatment to improve the adhesion between the fluorocarbon resinsheet 1 and the deposited inorganic oxide thin film 2. The improvementof adhesion can be achieved by forming, instead of forming thesurface-treated layer, a layer of a primer, an undercoater, an anchoringagent, an adhesive or a deposited undercoating material.

Suitable materials for forming the coating layer are, for example,composite resins containing a polyester resin, a polyamide resin, apolyurethane resin, an epoxy resin, a phenolic resin, a (meta)acrylicresin, a polyvinyl acetate resin, a polyolefin resin such as apolyethylene, a polypropylene or a copolymer or a resin obtained bymodifying one of those resins, a cellulose resin or the like as aprincipal component of a vehicle.

In the present invention, the composite resin may contain an ultravioletabsorber and/or an oxidation inhibitor for light resistance improvement.

The ultraviolet absorber absorbs detrimental ultraviolet rays insunlight, converts the energy of ultraviolet rays into harmless thermalenergy in its molecules to prevent active species that starts thephotodeterioration of polymers from being excited. One or some ofultraviolet absorbers, such as those of a benzophenone group, abenzotriazole group, a salicylate group, an acrylonitrile group,metallic complex salts, a hindered amine group and an inorganicultraviolet absorber, such as ultrafine titanium oxide powder (particlesize: 0.01 to 0.06 μm) or ultrafine zinc oxide powder (particle size:0.01 to 0.04 μm), may be used.

The oxidation inhibitor prevents the light deterioration or thermaldeterioration of polymers. Suitable oxidation inhibitors are, forexample, those of a phenol group, an amine group, a sulfur group, aphosphoric acid group and the like.

The ultraviolet absorber or the oxidation inhibitor may be anultraviolet absorbing polymer or an oxidation inhibiting polymerproduced by chemically bonding an ultraviolet absorber of thebenzophenone group or an oxidation inhibitor of the phenol group to theprincipal chains or the side chains of a polymer.

The ultraviolet absorber and/or the oxidation inhibitor content isdependent on the shape and density of particles and a preferableultraviolet absorber and/or the oxidation inhibitor content is in therange of about 0.1 to about 10% by weight.

The coating layer may be formed of a coating material of, for example, asolvent type, an aqueous type or an emulsion type by a roller coatingprocess, a gravure coating process, a kiss-roll coating process or thelike. The coating layer may be formed by a coating process subsequent toa fluorocarbon resin sheet forming process or a biaxial orientationprocess, or by an in-line coating process included in the film formingprocess or the biaxial orientation process.

The surface-treated layer 3 may be formed on one surface of thefluorocarbon resin sheet to protect the fluorocarbon resin sheet fromvapor deposition conditions for forming the deposited inorganic oxidethin film, to suppress yellowing, deterioration, shrinkage or cohesivefailure in a surface layer or an inner layer of the fluorocarbon resinsheet, and to improve the adhesion between the fluorocarbon resin sheetand the deposited inorganic oxide thin film. The surface-treated layer3, i.e., a deposition-resistant protective film, such as a depositedinorganic oxide thin film, may be formed by, for example, a chemicalvapor deposition process (CVD process), such as a plasma chemical vapordeposition process, a thermal chemical vapor deposition process or aphotochemical vapor deposition process, or a physical vapor depositionprocess (PVD process), such as a vacuum evaporation process, asputtering process or an ion plating process.

The thickness of the deposition-resistant protective film of siliconoxide or the like may be less than 150 Å. The deposition-resistantprotective film may be a nonbarrier film not having any barrier effectto inhibit the permeation of source gases and oxygen gas. concretely,the thickness of the deposition-resistant protective film is in therange of about 10 to about 100 Å, preferably, in the range of about 20to 80 Å, more preferably, in the range of about 30 to about 60 Å.

If the thickness is greater than 150 Å, more concretely 100 Å, 80 Å or60 Å, the fluorocarbon resin sheet is exposed to severe depositionconditions. Consequently, the fluorocarbon resin sheet turns yellow,cohesive failure occurs, the formation of a satisfactorydeposition-resistant protective film becomes difficult, and cracksdevelop in the film. If the thickness is less than 10 Å, 20 Å or 30 Å,the film is incapable of functioning as an effectivedeposition-resistant protective film.

The protective sheet of the present invention for a solar batterymodule, and the deposited inorganic oxide thin film 2 included in thesolar battery module will be described. The deposited inorganic oxidethin film may be a single-layer deposited inorganic oxide thin film, amultilayer film consisting of a plurality of deposited thin films of aninorganic oxide, or a composite film consisting of a plurality ofdeposited thin films respectively formed of different inorganic oxidesby a physical vapor deposition process, a chemical vapor depositionprocess, or both a physical vapor deposition process and a chemicalvapor deposition process.

The deposited inorganic oxide thin film formed by a physical vapordeposition process will be described. The physical vapor depositionprocess (PVD process) for forming the deposited inorganic oxide thinfilm may be, for example, a vacuum evaporation process, a sputteringprocess or anion plating process.

A deposited film can be deposited on a fluorocarbon resin sheet by avacuum evaporation process using a metal oxide as a source material, anoxidation vapor deposition process using a metal or a metal oxide,performing oxidation and depositing a metal oxide on the fluorocarbonresin sheet or a plasma-assisted oxidation vapor deposition processcarrying out a plasma-assisted oxidation.

In the foregoing process, the evaporation material may be heated by, forexample, a resistance heating method, a radio frequency heating methodor an electron beam (EB) heating method.

FIG. 8 is a diagrammatic view of a continuous vacuum evaporation systemfor forming the deposited inorganic oxide thin film by a physical vapordeposition process.

Referring to FIG. 8, in a continuous vacuum evaporation system 21, afluorocarbon resin sheet 1 unwound from a feed roll 23 disposed in avacuum chamber 22 is guided to a cooling coating drum 26 by guiderollers 24 and 25.

A source material 28, such as aluminum or aluminum oxide, contained in acrucible 27 is heated and vaporized, and the vaporized source material28 is deposited on the fluorocarbon resin sheet 1 wound around thecooling coating drum 26. When necessary, oxygen gas is blown through anoxygen gas supply opening 29 into the vacuum chamber 22. The evaporatedsource material 28 is deposited through masks 30 on the fluorocarbonresin sheet 1 in a deposited inorganic oxide thin film, such as analuminum oxide deposited thin film. The fluorocarbon resin sheet 1coated with the deposited inorganic oxide thin film, such as an aluminumoxide deposited thin film, is guided through guide rollers 25′ and 24′and is taken up in a take-up roll 31. A multilayer deposited inorganicoxide thin film consisting of a plurality of inorganic oxide films canbe formed on a fluorocarbon resin sheet by forming a first depositedinorganic oxide thin film on a fluorocarbon resin sheet by a firstprocessing cycle by the continuous vacuum evaporation system, andforming a second deposited inorganic oxide thin film on the firstdeposited inorganic oxide thin film by a second processing cycle by thesame continuous vacuum evaporation system. It is also possible to formthe multilayer deposited inorganic oxide thin film consisting of aplurality of deposited inorganic oxide thin films by successivelyprocessing the fluorocarbon resin sheet by a plurality of continuousvacuum evaporation systems similar to the foregoing continuous vacuumevaporation system.

Basically, the deposited inorganic oxide thin film may be a depositedthin film of ametal oxide, such as the oxide of silicon (Si), aluminum(Al), magnesium (Mg), Calcium (Ca), potassium (K), tin (Sn), sodium(Na), boron (B), titanium (Ti), lead (Pb), zirconium (Zr), yttrium (Y)or the like.

Preferable metal oxide deposited thin films are those of oxides ofsilicon (Si) and aluminum (Al).

The metal oxide deposited thin film can referred to as metal oxide, suchas silicon oxide, aluminum oxide and magnesium oxide. Those metal oxidesare represented by MO_(x) (SiO_(x), AlO_(x), MgO_(x)), where “x” isdependent on the valence of the metal.

The values of “x” re 0 to 2 for silicon (Si), 0 to 1.5 for aluminum(Al), 0 to 1 for magnesium (Mg), 0 to 1 for calcium (Ca), 0 to 0.5 forpotassium (K), 0 to 2 for tin (Sn), 0 to 0.5 for sodium (Na), 0 to 1.5for boron (B), 0 to 2 for titanium (Ti), 0 to 2 for lead (Pb), 0 to 2for zirconium (Zr) and 0 to 1.5 for yttrium (Y).

When x=0, the material is a metal, the film of the material is nottransparent and hence cannot be used. When the value of “x” is amaximum, the material is a complete oxide of the metal.

Although dependent on the kind of the metal or the metal oxide, thethickness of the inorganic oxide thin film is, for example, in the rangeof about 50 to about 2000 Å, preferably, about 100 to about 1000 Å. Amixture of different metals or a mixture of different metal oxides maybe used for forming the deposited inorganic oxide thin film. Thedeposited inorganic oxide thin film may be a film of a mixture ofdifferent inorganic oxides.

Further description will be given of the formation of the depositedinorganic oxide thin film by a chemical vapor deposition process. Thedeposited inorganic oxide thin film can be formed by a chemical vapordeposition process, such as a plasma chemical vapor deposition process,a thermal chemical vapor deposition process or a photochemical vapordeposition process.

More concretely, a deposited thin film of an inorganic oxide, such assilicon oxide can be formed by a low-temperature plasma chemical vapordeposition process using an evaporation monomer gas, such as an organicsilicon compound gas, as a source gas, an inert gas, such as argon gasor helium gas, as a carrier gas and oxygen gas as an oxygen supply gas.The low-temperature plasma chemical vapor deposition process is carriedout by a low-temperature plasma chemical vapor deposition system. Thelow-temperature plasma chemical vapor deposition system may use, forexample, a radio frequency plasma producing system, a pulse-wave plasmaproducing system or a microwave plasma producing system. It is desirableto use a radio frequency plasma producing system to produce a highlyactive, stable plasma.

A low-temperature plasma chemical vapor deposition process for formingthe deposited inorganic oxide thin film will concretely be described byway of example. FIG. 9 is a diagrammatic view of a low-temperatureplasma chemical vapor deposition system for carrying out thelow-temperature plasma chemical vapor deposition process for forming thedeposited inorganic oxide thin film.

Referring to FIG. 9, in a low-temperature plasma chemical vapordeposition system 41, a fluorocarbon resin sheet 1 unwound from a feedroll 43 disposed in a vacuum chamber 42 is guided to the circumferenceof a cooling electrode drum 45 by guide roller 44 at a predeterminedmoving speed.

Oxygen gas, an inert gas, a deposition monomer gas, such as an organicsilicon compound gas, and such are supplied from gas supply units 46 and47 and a source material volatilizing unit 48. The composition of amixed gas consisting of oxygen gas, the inert gas, the depositionmonomer gas and such is adjusted. The mixed gas of a predeterminedcomposition is supplied through a gas supply nozzle 49 into the vacuumchamber 42. A plasma 50 is produced on the fluorocarbon resin sheet 1wound round the cooling electrode drum 45 by glow discharge to deposit adeposited thin film of an organic oxide, such as silicon oxide, on thefluorocarbon resin sheet 1.

Predetermined power is supplied to the cooling electrode drum 45 by apower supply 51 disposed outside the vacuum chamber 42. A magnet 52 isdisposed near the cooling electrode drum 45 to promote the production ofthe plasma. The fluorocarbon resin sheet 1 provided with the depositedthin film of the inorganic oxide, such as silicon oxide, is guided to atake-up roll 54 by a guide roller 53 and is taken up on the take-up roll54. Thus, the deposited inorganic oxide thin film can be formed by theplasma chemical vapor deposition process. In FIG. 9, indicated at 55 isa vacuum pump.

The foregoing protective sheet and the foregoing method of fabricatingthe same are only examples and are not to be construed to limit thescope of the present invention.

The deposited inorganic oxide thin film is not limited to a single-layerdeposited inorganic oxide thin film but may be a multilayer filmconsisting of a plurality of deposited thin films of an inorganic oxide,or a composite film consisting of a plurality of deposited thin filmsrespectively formed of different inorganic oxides.

According to the present invention, a multilayer deposited inorganicoxide thin film consisting of a plurality of inorganic oxide films canbe formed on a fluorocarbon resin sheet by forming a first depositedinorganic oxide thin film on a fluorocarbon resin sheet by a firstprocessing cycle by the low-temperature plasma chemical vapor depositionsystem , and forming a second deposited inorganic oxide thin film on thefirst deposited inorganic oxide thin film by a second processing cycleby the same low-temperature plasma chemical vapor deposition system. Itis also possible to form the multilayer deposited inorganic oxide thinfilm consisting of a plurality of deposited inorganic oxide thin filmsby successively processing the fluorocarbon resin sheet by a pluralityof low-temperature plasma chemical vapor deposition systems similar tothe foregoing low-temperature plasma chemical vapor deposition system.

Monomer gases suitable for depositing the deposited thin film of aninorganic oxide, such as silicon oxide are those of1,1,3,3-tetramethyldisiloxane, hexamethyldisiloxane, vinyltrimethylsilane, methyl trimethylsilane, hexamethyldisilane,methylsilane, dimethylsilane, trimethylsilane, diethylsilane,propylsilane, phenylsilane, vinyl triethoxysilane, vinyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane,phenyltrimethoxysilane, methyltriethoxysilane,octamethylcyclotetrasiloxane and the like.

Among the foregoing organic silicon compounds,1,1,3,3-tetramethyldisiloxane or hexamethyldisiloxane is particularlypreferable in view of facility in handling and the characteristics of adeposited thin film formed by using the same as a source gas.

The inert gas is, for example, argon gas, helium gas or the like.

A silicon oxide deposited thin film formed by the foregoing processaccording to the present invention is a reaction product producedthrough the interaction of the monomer gas of an inorganic siliconcompound or the like and oxygen gas and firmly adhering to thefluorocarbon resin sheet and is dense and highly flexible. The siliconoxide deposited thin film is a continuous deposited thin film containingsilicon oxide indicated by SiO_(x)(x=0 to 2) as a principal component.

Preferably, the deposited thin film of silicon oxide contains adeposited thin film of silicon oxide indicted by a chemical formulaSiO_(x) (x=1.3 5o 1.9) as a principal component, in view of transparencyand barrier effect.

The value of x of SiO_(x) is dependent on the mole ratio between themonomer gas and oxygen gas, the energy of the plasma and the like.Generally, the gas permeability is lower, the deposited thin filmbecomes yellowish and the transparency of the deposited thin film islower when the value of x is smaller

The silicon oxide deposited thin film contains silicon (Si) and oxygen(O) as its essential constituent elements, and contains a very smallamount of carbon (C),hydrogen (H) or both carbon (C) and hydrogen (H).The thickness of the silicon oxide deposited thin film is in the rangeof 50 to 500 Å. The content ratio between the essential constituentelements and the minor elements varies continuously in a direction alongthe thickness.

The foregoing physical properties of the silicon oxide deposited thinfilm can be determined through the elementary analysis of the siliconoxide deposited thin film, in which the silicon oxide deposited thinfilm is analyzed through ion etching in the direction of the depth, bysurface analyzer, such as an x-ray photoelectron spectroscope for x-rayphotoelectron spectroscopy (XPS) or a secondary ion mass spectroscopefor secondary ion mass spectroscopy (SIMS).

Desirably, the thickness of the silicon oxide deposited thin film is inthe range of about 50 to about 2000 Å. More concretely, it is desirablethat the thickness is in the range of about 100 to 1000 Å. A thicknessgreater than 1000 Å, more specifically, greater than 2000 Å isundesirable, because a silicon oxide deposited thin film of such a greatthickness is liable to crack. A thickness less than 100 Å, morespecifically, less than 50 Å is undesirable, because a silicon oxidedeposited thin film of such a small thickness is incapable offunctioning as a barrier film.

The thickness can be measured by a fundamental parameter method using,for example, a fluorescent x-ray spectrometer (RIX2000, available fromK. K. Rigaku).

The thickness of the silicon oxide deposited thin film can be changed byincreasing the silicon oxide deposition rate by increasing therespective flow rates of the monomer gas and oxygen gas or by reducingthe deposition rate.

Each of the component deposited inorganic oxide thin films of theprotective sheet in accordance with the present invention for a solarbattery module, and the solar battery module in accordance with thepresent invention may be a composite film consisting of a plurality ofdeposited thin films of different inorganic oxides formed by using, forexample, both the physical vapor deposition process and the chemicalvapor deposition process in combination.

It is desirable to form such a composite film consisting of a pluralityof deposited thin films of different inorganic oxides by firstdepositing a dense, highly flexible, relatively hard-to-crack inorganicoxide thin film on a fluorocarbon resin sheet by a chemical vapordeposition process, and then depositing a deposited inorganic oxide thinfilm on the previously formed deposited inorganic oxide thin film by aphysical vapor deposition process.

Naturally, such a composite film consisting of a plurality of depositedthin films may be formed by first depositing an inorganic oxide thinfilm on a fluorocarbon resin sheet by a physical vapor depositionprocess, and then depositing a dense, highly flexible, relativelyhard-to-crack inorganic oxide thin film on the previously depositedinorganic oxide thin film by a chemical vapor deposition process.

An ordinary front surface protective sheet included in a solar batterymodule will be described. The front surface protective sheet must behighly transparent to sunlight and insulating, must be satisfactory inproperties including weather-resistant properties including heatresistance, light resistance and water resistance, wind endurance,hailstorm resistance, chemical resistance, moisture-proof property andsoil resistance, must be excellent in physical or chemical strength andtoughness, must be highly durable, and must be excellent in scratchresistance and impact absorbing property for the protection of solarcells as photvoltaic cells.

Glass sheets, and films or sheets of various resins includingfluorocarbon resins, polyamide resins (nylons), polyester resins,polyethylene resins, polypropylene resins, cyclic polyolefin resins,polystyrene resins, polymethyl methacrylate resins, polycarbonateresins, acetal resins and cellulose resins are possible materials forthe protective sheet.

The films or sheets of those resins may be uniaxially or biaxiallyoriented films or sheets.

The thickness of the films or sheets is in the range of about 12 toabout 200 μm. preferably, in the range of about 25 to about 150 μm.

Description will be given of the filler layer 12 underlying the frontsurface protective sheet in accordance with the present inventionincluded in the solar battery module. The filler layer 12 must betransparent to transmit and absorb incident sunlight and must beadhesive to the front surface protective sheet. The filler layer 12 mustbe thermoplastic to keep the surfaces of the solar cells, i.e.,photovoltaic cells, flat and smooth and must be excellent in scratchresistance and impact absorbing property to protect the solar cells,i.e., photovoltaic cells.

Materials suitable for forming the filler layer 12 are, for example,fluorocarbon resins, ethylene-vinyl acetate copolymers, ionomers,ethylene-acrylic acid or -methacrylic acid copolymers, polyethyleneresins, polypropylene resins, acid-modified polyolefin resins producedby modifying polyolefin resins, such as polyethylene resins orpolypropylene resins, by unsaturated carboxylic acid, such as acrylicacid, itaconic acid, maleic acid or fumaric acid, polyvinyl butyralresins, silicone resins, epoxy resins, (meta)acrylic resins, andmixtures of some of those resins.

The resin forming the filler layer 12 may contain additives including acrosslinking agent, a thermal oxidation inhibitor, a light stabilizer,an ultraviolet absorber and a photooxidation inhibitor by an amount thatwill not affect adversely to the transparency of the resin to improvethe weather-resistant properties including heat resistance, lightresistance and water resistance.

From the viewpoint of ensuring weather-resistant properties includinglight resistance, heat resistance and water resistance, desirablematerials for forming the filler layer on the sunlight receiving sideare fluorocarbon resins and ethylene-vinyl acetate resins.

The thickness of the filler layer is in the range of about 200 to about1000 μm, preferably, in the range of about 350 to about 600 μm.

The solar cells 13, i.e., photovoltaic cells, of the solar batterymodule will be described. The solar cells 13 may be known solar cells,such as crystalline silicon solar cells, polycrystalline silicon solarcells, amorphous silicon solar cells, copper-indium-selenide solarcells, compound semiconductor solar cells and the like.

The present invention may employ polycrystalline silicon thin-film solarcells, microcrystalline silicon thin-film solar cells, hybrid solarcells formed by combining crystalline silicon thin film solar cells andamorphous silicon solar cells.

The filler layer 14 underlying the solar cells of the solar batterymodule will be described. The filler layer 14, similarly to the fillerlayer 12 underlying the front surface protective sheet, must be adhesiveto the back surface protective sheet. The filler layer 14 must bethermoplastic to keep the surfaces of the solar cells, i.e.,photovoltaic cells, flat and smooth and must be excellent in scratchresistance and impact absorbing property to protect the solar cells,i.e., photovoltaic cells.

Differing from the filler layer 12 underlying the front surfaceprotective sheet, the filler layer 14 underlying the solar cells of thesolar battery module need not necessarily be transparent.

The filler layer 14, similarly to the filler layer 12 underlying thefront surface protective sheet, may be formed of one of materialsincluding fluorocarbon resins, ethylene-vinyl acetate copolymers,ionomers, ethylene-acrylic acid or -methacrylic acid copolymers,polyethylene resins, polypropylene resins, acid-modified polyolefinresins produced by modifying polyolefin resins, such as polyethyleneresins or polypropylene resins, by unsaturated carboxylic acid, such asacrylic acid, itaconic acid, maleic acid or fumaric acid, polyvinylbutyral resins, silicone resins, epoxy resins, (meta)acrylic resins, andmixtures of some of those resins.

The resin forming the filler layer 14 may contain additives including acrosslinking agent, a thermal oxidation inhibitor, a light stabilizer,an ultraviolet absorber and a photooxidation inhibitor by an amount thatwill not affect adversely to the transparency of the resin to improvethe weather-resistant properties including heat resistance, lightresistance and water resistance.

The thickness of the filler layer is in the range of about 200 to about1000 μm, preferably, in the range of about 350 to about 600 μm.

An ordinary back surface protective sheet included in a solar batterymodule will be described. The back surface protective sheet must be aninsulating resin film or sheet. The back surface protective sheet mustbe satisfactory in weather-resistant properties including heatresistance, light resistance and water resistance, must be excellent inchemical or physical strength and toughness, and must be excellent inscratch resistance and impact absorbing property for the protection ofsolar cells as photvoltaic cells.

Films or sheets of various resins including polyamide resins (nylons),polyester resins, polyethylene resins, polypropylene resins, cyclicpolyolefin resins, polystyrene resins, polycarbonate resins, acetalresins, cellulose resins (meta)acrylic resins and fluorocarbon resinsare possible materials for the protective sheet.

The films or sheets of those resins may be uniaxially or biaxiallyoriented films or sheets.

The thickness of the films or sheets is in the range of about 12 toabout 200 μm, preferably, in the range of about 25 to about 150 μm.

The solar battery module of the present invention may be provided withan additional weather-resistant sheet for the improvement of thestrength, weather resistance, scratch resistance and the durability ofthe solar battery module. Possible materials for forming the additionalweather-resistant sheet are, for example, low-density polyethylenes,medium-density polyethylenes, high-density polyethylenes, linearlow-density polyethylenes, polypropylenes, ethylene-propylenecopolymers, ethylene-vinyl acetate copolymers, ionomers, ethylene-ethylacrylate copolymers, ethylene-acrylate or -methacrylate copolymers,methyl pentene polymers, polybutene resins, polyvinyl chloride resins,polyvinyl acetate resins, polyvinylindene chloride resins, vinylchloride-vinylidene chloride copolymers, poly(meta)acrylic resins,polyacrylonitrile resins, polystyrene resins, acrylonitrile-styrenecopolymers (AS resins), acrylonitrile-butadiene-styrene copolymers (ABSresins), polyester resins, polyamide resins, polycarbonate resins,polyvinyl alcohol resins, saponified ethylene-vinyl acetate copolymers,fluorocarbon resins, diene resins, polyacetal resins, polyurethaneresins, nitrocellulose, polymers obtained by the polymerization ofcyclopentadiene, cyclopentadiene derivatives, dicyclopentadiene,dicyclopentadiene derivatives, cyclohexadiene, cyclohexadienederivatives, norbornadiene, norbornadiene derivatives and cyclic dienes,transparent cyclic polyolefin resins produced by the copolymerization ofthe cyclic diene, and one or some of olefin monomers including ethylene,propylene, 4-methyl-1-pentene, styrene, butadiene, isoprene and thelike, and other known resins. The additional weather-resistant sheet maybe disposed on the deposited inorganic oxide thin film.

The films or sheets of those resins may be nonoriented, uniaxiallyoriented or biaxially oriented.

There is no restriction on the thickness of those films or sheets; thethickness of the films or sheets may be in the range of severalmicrometers to about 300 am.

The films or sheets may be extruded films, blown films or coating films.

A method of fabricating the solar battery module in accordance with thepresent invention using the foregoing materials will be describedhereinafter. The method of fabricating the solar battery module uses theprotective sheet in accordance with the present invention for a solarbattery module as the front surface protective sheet or the back surfaceprotective sheet of the solar battery module. The solar battery moduleis fabricated by superposing the protective sheet, the filler layer, aphotovoltaic layer of the solar cells, i.e., photovoltaic cells, thefiller layer and a generally known back surface protective sheet in thatorder in a superposed structure, and subjecting the superposed structureto a generally known forming process, such as a lamination process, inwhich those component layers of the superposed structure are broughtinto close contact by vacuum and are bonded together by hot pressing.The deposited inorganic oxide thin film of the front surface protectivesheet faces inside. When necessary, other layers are interposed betweenthose component layers.

When necessary, layers of a hot-melt adhesive, a solvent adhesive, aphotocurable adhesive or the like containing a (meta)acrylic resin, anolefin resin, a vinyl resin or the like as a principal component of itsvehicle may be formed between the component layers to enhance theadhesion between the adjacent component layers.

When necessary, the contact surfaces of the adjacent component layersmay be pretreated by a pretreatment process, such as a corona dischargeprocess, ozonizing process, a low-temperature plasma process usingoxygen gas or nitrogen gas, an atmospheric pressure plasma process, glowdischarge process, an oxidation process using a chemical or the like toenhance the adhesion between the contact surfaces.

A pretreatment layer of a primer, an undercoating material, an adhesiveor an anchoring agent or the like may be formed on the contact surfacesof the adjacent component layers for a surface pretreatment process.

The pretreatment layer may be formed of a resin compound containing as aprincipal component of its vehicle one of resins including, for example,polyester resins, polyamide resins, polyurethane resins, epoxy resins,phenolic resins, (meta)acrylic resins, polyvinyl acetate resins,polyolefin resins, such as polyethylene resins or polypropylene resins,copolymers or modifications of polyolefin resins and cellulose resins.

The coating layer may be formed of a coating material of a solvent type,an aqueous type or an emulsion type by a roll coating process, a gravurecoating process, a kiss-roll coating process or the like.

The surface pretreatment process may form a deposited inorganic oxidethin film of a thickness in the range of about 20 to about 100 Å,preferably, in the range of about 30 to 60 Å not having barrier effectto improve the adhesion between the adjacent component layers by aprocess similar to the foregoing process for forming the depositedinorganic oxide thin film.

EXAMPLES

Examples of the first embodiment will be described hereinafter.

Example 1

(1) A roll of a 50 μm thick polyvinyl fluoride sheet (PVF sheet), i.e.,base sheet, was mounted on a feed roll of a continuous vacuumevaporation system. The polyvinyl fluoride sheet was unwound and woundaround a coating drum and a 500 Å thick deposited aluminum oxide thinfilm was deposited on a treated surface of the polyvinyl fluoride sheettreated for adhesion improvement by a reactive vacuum evaporationprocess of an electron beam (EB) heating system. Aluminum was used as anevaporation source and oxygen gas was supplied to the continuous vacuumevaporation system.

Deposition Conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

EB power: 40 kW

Sheet moving speed: 600 m/min

(2) A protective sheet in accordance with the present invention for asolar battery module was completed by subjecting the 500 Å thickdeposited aluminum oxide thin film formed on the surface of thepolyvinyl fluoride sheet to a glow-discharge plasma process to form aplasma-processed surface. The glow-discharge plasma process was carriedout by a glow-discharge plasma producing apparatus of 1500 W in plasmaoutput immediately after the deposition of the 500 Å thick depositedaluminum oxide thin film. In the glow-discharge plasma process, anoxygen/argon mixed gas of 19/1 in O₂/Ar ratio was supplied so that thepressure of the oxygen/argon mixed gas is maintained at 6×10⁻⁵ torr andthe processing speed was 420 m/min.

(3) A solar battery module was fabricated by using the protective sheetthus fabricated. The protective sheet, a 400 μm thick ethylene-vinylacetate copolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the plasma-processed deposited aluminum oxide thinfilm facing inside and the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 2

(1) A roll of a 50 μm thick polyvinyl fluoride film (PVF film), i.e.,base sheet, was mounted on a feed roll of a plasma chemical vapordeposition system. A 500 Å thick deposited silicon oxide thin film wasdeposited on a treated surface of the polyvinyl fluoride film treatedfor adhesion improvement under the following conditions.

Deposition Conditions:

Reaction gas mixing ratio: Hexamethyldisiloxane/oxygen/helium=1/10/10(Unit: slm)

Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

Vacuum in deposition chamber: 6.0×10⁻² mbar

Power supplied to cooling electrode drum: 20 kW

Film moving speed: 80 m/min

Surface for vapor deposition: Corona-processed surface

(2) A protective sheet in accordance with the present invention for asolar battery module was completed by subjecting the 500 Å thickdeposited silicon oxide thin film formed on the surface of the polyvinylfluoride film to a corona discharge process to form a corona-processedsurface and to increase the surface tension of the deposited siliconoxide thin film from 35 dyne to 60 dyne. Corona discharge power was 10kW and the sheet was moved at a moving speed of 100 m/min.

(3) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the corona-processed deposited silicon oxide thin film facinginside and the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 3

(1) A roll of a 50 μm thick polyvinyl fluoride film (PVF film)containing an ultraviolet absorber was mounted on a feed roll of aplasma chemical vapor deposition system. A 500 Å thick deposited siliconoxide thin film was deposited on a treated surface of the polyvinylfluoride film treated for adhesion improvement under the followingconditions.

Deposition Conditions:

Reaction gas mixing ratio: Hexamethyldisiloxane/oxygen/helium=1/10/10(Unit: slm)

Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

Vacuum in deposition chamber: 6.0×10⁻² mbar

Power supplied to cooling electrode drum: 20 kW

Film moving speed: 80 m/min

Surface for deposition: Corona-processed surface

The surface of the 500 Å thick deposited silicon oxide thin film formedon the polyvinyl fluoride film was subjected to a corona dischargeprocess to form a corona-processed surface to increase the surfacetension of the deposited silicon oxide thin film, from 35 dyne to 60dyne. Corona discharge power was 10 kW and the sheet was moved at amoving speed of 100 m/min.

(2) A roll of the polyvinyl fluoride film provided with thecorona-processed deposited silicon oxide thin film was mounted on a feedroll of a continuous vacuum evaporation system. The polyvinyl fluoridefilm was unwound and wound around a coating drum and a 500 Å thickdeposited aluminum oxide thin film was deposited on the corona-processedsurface of the deposited silicon oxide thin film formed on the polyvinylfluoride film by a reactive vacuum evaporation process of an electronbeam (EB) heating system. Aluminum was used as an evaporation source andoxygen gas was supplied to the continuous vacuum evaporation system.

Deposition Conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

EB power: 40 kW

Film moving speed: 600 m/min

A protective sheet in accordance with the present invention for a solarbattery module was completed by subjecting the 500 Å thick depositedaluminum oxide thin film formed on the surface of the polyvinyl fluoridesheet to a glow-discharge plasma process to form a plasma-processedsurface. The glow-discharge plasma process was carried out by aglow-discharge plasma producing apparatus of 1500 W in plasma outputimmediately after the deposition of the 500 Å thick deposited aluminumoxide thin film. In the glow-discharge plasma process, an oxygen/argonmixed gas of 19/1 in O₂/Ar ratio was supplied so that the pressure ofthe oxygen/argon mixed gas is maintained at 6×10⁻⁵ torr and theprocessing speed was 420 m/min.

(3) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The protectivesheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μmthick biaxially oriented polyethylene terephthalate film provided withan array of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and a 50 μm thick biaxially orientedpolyethylene terephthalate film were superposed in that order with theplasma-processed deposited aluminum oxide thin film facing inside andthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the front surfaceprotective sheet. Those component layers were laminated by usingadhesive layers of an acrylic resin to complete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride film (PVF film).

Example 4

(1) Protective sheets that are the same as the protective sheet inExample 1 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the plasma-processed deposited aluminum oxide thin films ofthe front surface and the back surface protective sheet facing insideand with the surface of the 38 μm thick polyethylene terephthalate filmprovided with the solar cells facing the front surface protective sheet,and laminating those component layers by using adhesive layers of anacrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 50 μm thick fluorocarbon resin sheets ofan ethylene-tetrafluoroethylene copolymer (ETFE) were used instead ofthe 50 μm thick polyvinyl fluoride sheets (PVF sheet).

Example 5

(1) Protective sheets that are the same as the protective sheet inExample 2 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the plasma-processed deposited silicon oxide thin films ofthe front surface and the back surface protective sheet facing insideand with the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 50 μm thick fluorocarbon resin sheets ofan ethylene-tetrafluoroethylene copolymer (ETFE) were used instead ofthe 50 μm thick polyvinyl fluoride sheets (PVF sheet).

Example 6

(1) Protective sheets that are the same as the protective sheet inExample 3 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the plasma-processed deposited aluminum oxide thin films ofthe front surface and the back surface protective sheet facing insideand with the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 50 μm thick fluorocarbon resin sheets ofan ethylene-tetrafluoroethylene copolymer (ETFE) containing anultraviolet absorber were used instead of the 50 μm thick polyvinylfluoride sheets (PVF sheet) containing the ultraviolet absorber.

Example 7

(1) A protective sheet that is the same as the protective sheet inExample 1 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a3 mm thick glass sheet, a 400 μm thick ethylene-vinyl acetate copolymersheet, a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the plasma-processed deposited aluminum oxidethin film of the back surface protective sheet facing inside and withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the 3 mm thickglass sheet, and laminating those component layers by using adhesivelayers of an acrylic resin.

(2) A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 50 μm thick fluorocarbon resin sheetof an ethylene-tetrafluoroethylene copolymer (ETFE) was used instead ofthe 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 8

(1) A protective sheet that is the same as the protective sheet inExample 2 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with thecorona-processed deposited silicon oxide thin film of the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick polyvinyl fluoride sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

(2) A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 50 μm thick fluorocarbon resin sheetof an ethylene-tetrafluoroethylene copolymer (ETFE) was used instead ofthe 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 9

(1) A protective sheet that is the same as the protective sheet inExample 3 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with theplasma-processed deposited aluminum oxide thin film of the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick polyvinyl fluoride sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

(2) A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 50 μm thick fluorocarbon resin sheetof an ethylene-tetrafluoroethylene copolymer (ETFE) was used instead ofthe 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 10

(1) A roll of a 50 μm thick fluorocarbon resin sheet of aethylene-tetrafluoroethylene copolymer (ETFE) was mounted on a feed rollof a plasma chemical vapor deposition system. A 50 Å thick depositedsilicon oxide thin film as a surface layer was deposited on a treatedsurface of the fluorocarbon resin sheet treated for adhesion improvementunder the same conditions as those in Example 2.

Subsequently, a 800 Å thick deposited silicon oxide thin film was formedon the surface layer by the same process as that in Example 2. Thesurface of the 800 Å thick deposited silicon oxide thin film wassubjected to the same corona discharge process as in Example 2 toincrease the surface tension of the same from 35 dyne to 60 dyne and toform a protective sheet having a corona-processed surface in accordancewith the present invention for a solar battery module.

(2) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the corona-processed deposited silicon oxide thin film facinginside and the surface of the 38μm thick biaxially oriented polyethyleneterephthalate film provided with the solar cells facing the frontsurface protective sheet. Those component layers were laminated by usingadhesive layers of an acrylic resin to complete a solar battery module.

(3) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick polyvinyl fluoridesheet (PVF sheet) was used instead of the 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer(ETFE).

Example 11

(1) Protective sheets that are the same as the protective sheet inExample 10 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the corona-processed deposited silicon oxide thin films ofthe front surface and the back surface protective sheet facing insideand with the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 50 μm thick polyvinyl fluoride sheets(PVF sheets) were used instead of the 50 μm thick fluorocarbon resinsheets of an ethylene-tetrafluoroethylene copolymer (ETFE).

COMPARATIVE EXAMPLE 1

A solar battery module was fabricated by superposing a 3 mm thick glasssheet, i.e., base sheet, as a back surface protective sheet, a 400 μmthick ethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with an array ofamorphous silicon solar cells, a 400 μm thick ethylene-vinyl acetatecopolymer sheet and a 50 μm thick biaxially oriented polyethyleneterephthalate film in that order with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick biaxially orientedpolyethylene terephthalate film, and laminating those component layersby using adhesive layers of an acrylic resin.

COMPARATIVE EXAMPLE 2

A solar battery module was fabricated by superposing a 50 μm thickpolyvinyl fluoride sheet (PVF sheet), i.e., base sheet, as a frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film in that orderwith the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing the 50μm thick polyvinyl fluoride sheet, and laminating those component layersby using adhesive layers of an acrylic resin.

COMPARATIVE EXAMPLE 3

A solar battery module was fabricated by superposing a 50 μm thickpolyvinyl fluoride sheet (PVF sheet), i.e., base sheet, as a frontsurface protective sheet, a 400 0 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick polyvinyl fluoride sheet (PVF sheet) as a back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin. andlaminating those component layers by using adhesive layers of an acrylicresin.

EXPERIMENTS

The protective sheets in Examples 1 to 11 of the present invention andthose in comparative examples 1 to 3 were subjected to totaltransmittance measurement. The solar battery modules in Examples 1 to 11and comparative examples 1 to 3 were subjected to solar battery moduleevaluation tests.

(1) Total Transmittance Measurement

Total transmittance (%) of each of the protective sheets in Examples 1to 11 and Comparative examples 1 to 3 against the total transmittance ofthe base sheet as a reference total transmittance was measured by acolor computer.

(2) Solar Battery Module Evaluation Tests

The solar battery modules were subjected to environmental tests inconformity to conditions specified in JIS C8917-1989. Photovoltaicoutput of the solar battery modules was measured before and afterenvironmental tests.

(3) Moisture Permeability and Oxygen Permeability

The moisture permeabilities of the protective sheets in Examples 1 to 11and Comparative examples 1 to 3 were measured in an atmosphere of 400°C. and 90% RH by a moisture permeability measuring apparatus (PERMATRAN,MOCON, USA). The oxygen permeabilities of the protective sheets inExamples 1 to 11 and Comparative examples 1 to 3 were measured in anatmosphere of 23° C. and 90% RH by an oxygen permeability measuringapparatus (OXTRAN: MOCON, USA). Measured data is tabulated in Table 1-1.

TABLE 1-1 Total Moisture Oxygen Output trans- permea- permea- reductionmittance bility Bility Ratio (%) (g/m²/24 hr) (cc/m²/24 hr/atm) (%)Example 1 93 0.9 1.1 3 Example 2 92 0.6 0.5 2 Example 3 93 0.6 0.7 2Example 4 93 0.9 1.1 1 Example 5 92 0.6 0.4 1 Example 6 93 0.6 0.7 1Example 7 93 0.9 1.1 2 Example 8 92 0.6 0.5 5 Example 9 93 0.6 0.7 5Example 10 91 0.1 0.4 1 Example 11 91 0.1 0.3 1 Comparative 89 25.0 80.018 Example 1 Comparative 93 27.0 28.0 15 Example 2 Comparative 93 27.028.0 12 Example 3

In table 1-1, moisture permeability is expressed in a unit ofg/m²/day·40° C.·100% RH (relative humidity), and oxygen permeability isexpressed in a unit of cc/m²/day·23° C.·90% RH.

As obvious from Table 1-1, the protective sheets in Examples 1 to 11have high total transmittances, respectively, and are excellent inmoisture impermeability and oxygen impermeability.

The output reduction ratios of the solar battery modules employing theprotective sheets in Examples 1 to 11 were low.

The protective sheets in Comparative examples 1 to 3 had high totaltransmittances, respectively. However, the moisture impermeabilities andthe oxygen impermeabilities of the protective sheets in Comparativeexamples 1 to 3 were low. Consequently, the output reduction ratios ofthe solar battery modules employing the protective sheets in Comparativeexamples 1 to 3 were high.

As apparent from the foregoing description, the present invention takesnotice of the properties of glass sheets that are used as the frontsurface protective sheets of solar battery modules, uses a fluorocarbonresin sheet as a base sheet, fabricates a protective sheet for a solarbattery module by forming a transparent, vitreous deposited inorganicoxide thin film, such as a silicon oxide thin film or an aluminum oxidethin film, on one of the surfaces of the fluorocarbon resin sheet; theprotective sheet thus fabricated is used as the front surface protectivesheet or the back surface protective sheet of a solar battery module;the solar battery module is fabricated by, for example, superposing theprotective sheet as a front surface protective sheet, a filler layer, afilm provided with solar cells, i.e., photovoltaic cells, a filler layerand an ordinary back surface protective sheet for a solar battery modulein that order in a superposed structure with the deposited inorganicoxide thin film facing inside, bringing the component layers of thesuperposed structure into close contact by vacuum and bonding togetherthose component layers by a lamination process using hot pressing; andthe protective sheet transmits sunlight at a high transmittance, isexcellent in strength, weather resistance, heat resistance, waterresistance, light resistance, wind endurance, hailstorm resistance,chemical resistance, moisture resistance and soil resistance, has a highimpermeability to moisture and oxygen, limits performance degradationdue to aging to the least extent, very durable, has excellent protectiveability, and can be used for the stable fabrication of a low-cost, safesolar battery module.

Other examples of the present invention and comparative examples will bedescribed hereinafter.

Example 12

Front Surface Protective Sheet

A transparent 25 μm thick ETFE film was used as a weather-resistantfilm. A 500 Å thick silicon oxide (SiO,)thin film (gas-barrier layer)was deposited on one surface of the ETFE film by a PE-CVD process. Afront surface protective sheet in Example 1 was fabricated by forming a250 μm thick adhesive layer of a composite material prepared byhomogeneously mixing 100 parts by weight of an ethylene-vinyl acetatecopolymer having a vinyl acetate content of 35% by weight, 2 parts byweight of a crosslinking agent (DCP: dicumylperoxide) and 3 parts byweight of ultraviolet absorber (2,4-dihydroxybenzophenone) at 110° C. onthe ETFE film by a calender coating process.

Back Surface Protective Sheet

Two white 38 μm thick PVF films and a 20 μm thick aluminum foil (gasbarrier layer) were laminated by a dry lamination process to form alaminated structure of (38 μm thick white PVF film)/(20 μm thickaluminum foil)/(38 μm thick white PVF film). A back surface protectivesheet in Example 1 was fabricated by forming a 250 μm thick compositeresin layer of a composite material prepared by homogeneously mixing 100parts by weight of an ethylene-vinyl acetate copolymer having a vinylacetate content of 35% by weight, 1 part by weight of a crosslinkingagent (DCP: dicumilperoxyd), 2 parts by weight of ultraviolet absorber(2,4-dihydroxybenzophenone) and 25 parts by weight of titanium oxide(white pigment) at 120° C. on the ETFE film by a calender coatingprocess.

Example 13

Front Surface Protective Sheet

A transparent 25 μm thick PVF film was used as a weather-resistant film.A 400 Å thick aluminum oxide thin film (gas-barrier layer) was depositedon one surface of the PVF film by a PVD process. A coating liquid of aninorganic-organic hybrid material prepared by mixing 5 parts by weightof tetraethoxysilane and 95 parts by weight of an ethylene-vinyl alcoholcopolymer was applied in a coating layer of 3 g/m² to the aluminum oxidethin film by a gravure coating process, and the coating layer washot-dried to complete a composite gas-barrier layer. A 200 μm thickadhesive layer was formed on the composite gas-barrier layer byextruding a composite resin prepared by homogeneously mixing 100 partsby weight of an ethylene-vinyl acetate having a vinyl acetate content of30% by weight, 1.5 parts by weight of a TBPH(2,5-dimethyl-2,5-di(t-butylperoxy)hexane), i.e., a crosslinking agent,2 parts by weight of TAC (triallylcyanurate), i.e., a crosslinkingauxiliary, and three parts by weight of silane coupling agent at 110° C.on the composite gas-barrier layer by an extrusion coating process tocomplete a front surface protective sheet in Example 2 for a solarbattery module.

Back Surface Protective Sheet

Two white 25 μm thick weather-resistant polyethylene terephthalate films(hereinafter referred to as “white weather-resistant PET films”)and a 20μm thick aluminum foil (gas barrier layer) were laminated by a drylamination process to form a laminated structure of (25 μm thick whiteweather-resistant PET film)/(20 μm thick aluminum foil)/(25 μm thickwhite weather-resistant PET film). A 200 μm thick adhesive layer of acomposite material prepared by homogeneously mixing 100 parts by weightof an ethylene-vinyl acetate copolymer having a vinyl acetate content of30% by weight, 1.5 part by weight of a TBPH(2,5-dimethyl-2,5-di(t-butylperoxy)hexane), i.e., a crosslinking agent,1.5 parts by weight of TAC (triarylcyanurate), i.e., a crosslinkingauxiliary, and 2 parts by weight of silane coupling agent at 110° C. wasformed on one surface of the laminated structure by an extrusion coatingprocess to complete a back surface protective sheet in Example 13 for asolar battery module.

COMPARATIVE EXAMPLE 4

Front Surface Protective Sheet

A front surface protective sheet in Comparative example 4 is the same asthe front surface protective sheet in Example 12, except that thedeposited silicon oxide (SiO_(x)) thin film, i.e., a gas-barrier layer,is omitted.

Back Surface Protective Sheet

A back surface protective sheet in Comparative example 4 is the same asthe back surface protective sheet in Example 12, except that thealuminum foil sandwiched between the two white PVF films is omitted.

Tests and Test Results

The front surface protective sheets and the back surface protectivesheets in Examples 12 and 13 and Comparative example 4 for solar batterymodules were subjected to the following tests. Test results aretabulated in Tables 1-2 and 1-3.

(1) Moisture permeabilities in an atmosphere of 40° C. and 90% RH andoxygen permeabilities in an atmosphere of 25° C. and 100% RH of theprotective sheets were measured by a moisture permeability measuringapparatus (MOCON PERMATAN, Modern Control) and an oxygen permeabilitymeasuring apparatus (MOCON OXTRAN, Modern Control). Measured data isshown in Table 1-2.

TABLE 1-2 Moisture Oxygen Test permeability permeability Sample (g/m²/24hr) (cc/m²/24 hr/atm) Example 12 Front surface 0.9 1.1 protective filmBack surface ≦0.1 ≦0.1 protective film Example 13 Front surface 0.2 0.4protective film Back surface ≦0.1 ≦0.1 protective film Comparative Frontsurface 18 43 Example 4 protective film Back surface 4.9 5.2 protectivefilm

In table 1-2, moisture permeability is expressed in a unit ofg/m²·atm·day, and oxygen permeability is expressed in a unit ofcc/m²·atm·day.

(2) Solar battery modules in Examples 12 and 13 and Comparative example4 were fabricated by combining the front surface protective sheets andthe back surface protective sheets in Examples 12 and 13 and Comparativeexample 4 with solar batteries employing a microcrystalline silicon thinfilm formed by a PE-CVD process by a vacuum lamination process. Thesolar battery modules were subjected to tests to evaluate theirperformance and long-term stability, in which photoelectric conversionefficiency η (%) and fill factor (FF) were measured in an initial stateand in a state after irradiation with 1 sun, at 50° C. for 2000 hr.Measured data is tabulated in Table 1-3.

TABLE 1-3 Characteristic of solar battery State after exposure Initialstate to 1 sun, 50° C., 2000 hr Conversion Conversion efficiencyefficiency η (%) FF η (%) FF Example 12 10.5 0.75 10.3 0.73 Example 1310.4 0.75 10.4 0.75 Comparative 10.5 0.75 9.0 0.65 Example 4

As obvious from the measured data shown in Tables 1-2 and 1-3, theprotective sheets in Examples 12 and 13, which comprise the gas-barrierlayer in addition to the weather-resistant film and the adhesive layers,are excellent in strength, weather resistance and heat resistance, havevery small moisture permeabilities and oxygen permeabilities,respectively, and are highly gas-impermeable.

The solar battery modules in Examples 12 and 13 fabricated bysandwiching the microcrystalline silicon thin film, which deteriorateseasily in an atmosphere containing moisture or oxygen, between theprotective sheets in Example 12 or 13 maintains satisfactoryphotoelectric conversion efficiency and FF after being irradiated by 1sun at 50° C. for 2000 hr. Thus, the solar battery modules in Examples12 and 13 are excellent in long-term stability.

SECOND EMBODIMENT

Protective sheets for solar battery modules, and solar battery modulesin a second embodiment according to the present invention will bedescribed with reference to FIGS. 1 to 9 which have been used fordescribing the first embodiment.

Referring to FIG. 1, a protective sheet A in accordance with the presentinvention for a solar battery module has a basic structure constructedby forming a deposited inorganic oxide thin film 2 on one of thesurfaces of a weather-resistant sheet 1 of a cyclic polyolefin resin.

As shown in FIG. 3, a protective sheet A₁ in an example of the presentinvention for a solar battery module is formed by forming a multilayerfilm 4 consisting of at least two deposited inorganic oxide thin films 2on one of the surfaces of a cyclic polyolefin resin sheet 1.

As shown in FIG. 4 a protective sheet A₃ in another example of thepresent invention for a solar battery module comprises a cyclicpolyolefin resin sheet 1 and a composite film 5 formed on one of thesurfaces of the cyclic polyolefin resin sheet 1. The composite film 5consists of a first deposited inorganic oxide thin film 2 a formed onone of the surfaces of the cyclic polyolefin resin sheet 1 by a chemicalvapor deposition process, and a second deposited inorganic oxide thinfilm 2 b of an inorganic oxide different from that of the firstdeposited inorganic oxide film 2 a, formed on the first depositedinorganic oxide thin film 2 a by a physical vapor deposition process.

Those protective sheets are only examples of the protective sheet inaccordance with the present invention and the present invention is notlimited thereto.

For example, in the protective sheet A₃ shown in FIG. 4, a depositedinorganic thin film may be formed first on the surface of the cyclicpolyolefin resin sheet 1 a physical vapor deposition process, and thenanother deposited inorganic oxide thin film may be formed by a chemicalvapor deposition process.

A solar battery module employing this protective sheet A embodying thepresent invention and shown in FIG. 1 will be described by way ofexample. Referring to FIG. 5, a solar battery module T employs theprotective sheet A shown in FIG. 1 as its front surface protective sheet11(A). The solar battery module T is fabricated by superposing theprotective sheet 11(A), a filler layer 12, a photovoltaic layer 13 ofsolar cells, a filler layer 14 and a generally known back surfaceprotective sheet 15 in that order in a superposed structure, andsubjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing. The deposited inorganic oxide thinfilm 2 of the protective sheet 11 faces inside.

Another solar battery module T₁ shown in FIG. 6 employs the protectivesheet A shown in FIG. 1 as its back surface protective sheet 16. Thesolar battery module T₁ is fabricated by superposing a generally knownfront surface protective sheet 17, a filler layer 12, a photovoltaiclayer 13 of solar cells, a filler layer 14 and the protective sheet16(A) in that order in a superposed structure, and subjecting thesuperposed structure to a generally known forming process, such as alaminating process, in which those component layers of the superposedstructure are brought into close contact by vacuum and are bondedtogether by hot pressing. The deposited inorganic oxide thin film 2 ofthe protective sheet 16 faces inside.

A third solar battery module T₂ shown in FIG. 7 employs the protectivesheet A shown in FIG. 1 as its front surface protective sheet 11 and itsback surface protective sheet 16. The solar battery module T₂ isfabricated by superposing the front surface protective sheet 11(A), afiller layer 12, a photovoltaic layer 13 of solar cells, a filler layer14 and the protective sheet 16(A) in that order in a superposedstructure, and subjecting the superposed structure to a generally knownforming process, such as a lamination process, in which those componentlayers of the superposed structure are brought into close contact byvacuum and are bonded together by hot pressing. The deposited inorganicoxide thin film 2 of each of the protective sheets 11 and 16 facesinside.

The foregoing protective sheets in accordance with the present inventionand the foregoing solar battery modules employing those protectivesheets are examples intended to illustrate the invention and not to beconstrued to limit the scope of the invention.

For example, the protective sheets shown in FIGS. 3 and 4 can be appliedto solar battery modules of various types. The foregoing solar batterymodules may comprise additional layers for sunlight absorption,reinforcement or the like.

Materials for and methods of fabricating the protective sheets inaccordance with the present invention and the solar battery modulesemploying those protective sheets will be described. It is desirablethat the cyclic polyolefin resin film or sheet for the protective sheetsembodying the present invention and the solar battery modules employingthose protective sheets has a high sunlight transmittance because thesolar battery absorbs sunlight and generates power by its photovoltaiceffect.

It is desirable that the cyclic polyolefin resin film or sheet isexcellent in mechanical or chemical strength, excellent in weatherresistance, heat resistance, water resistance, light resistance, windendurance, hailstorm resistance, chemical resistance and piercingstrength. It is particularly desirable that the cyclic polyolefin resinfilm or sheet is excellent in weather resistance and moistureimpermeability that prevents the permeation of oxygen and the like, hasa high surface hardness, is excellent in soil resistance that preventsthe accumulation of soil and dust thereon, is very durable and has ahigh protective ability.

It is desirable that the cyclic polyolefin resin film or sheet iscapable of withstanding conditions for forming a deposited inorganicoxide thin film thereon, does not spoil the characteristics thereof andthe deposited inorganic oxide thin film deposited thereon, is capable offirmly adhering to the deposited inorganic oxide thin film and ofsatisfactorily holding the same thereon.

The present invention may employ transparent cyclic polyolefin films orsheets of, for example, cyclopentadiene, cyclopentadiene derivatives,dicyclopentadiene, dicyclopentadiene derivatives, cyclohexadiene,cyclohexadiene derivatives, norbornadiene, norbornadiene derivatives,polymers produced through the polymerization of cyclic dienes,copolymers of cyclic dienes and one or some of ethylene, propylene,4-methyl-1-pentene, styrene, butadiene, isoprene and the like.

Among those transparent cyclic polyolefin resin films or sheets, film orsheets of polycyclopentadienes of cyclic dienes includingcyclopentadiene, cyclopentadiene derivatives, dicyclopentadiene,dicyclopentadiene derivatives, norbornadiene and norbornadienederivatives are excellent in properties including weather resistance,water resistance and transparency, and are particularly preferable fromthe view point of sunlight transmission.

The protective sheets of the solar battery modules using the cyclicpolyolefin resin film or sheet utilizes the excellent properties of thecyclic polyolefin resin sheet including mechanical properties, opticalproperties and properties including weather resistance, heat resistanceand water resistance, moisture impermeability, soil resistance, chemicalresistance and piercing strength. The protective sheet is equal to theglass sheet used as the conventional protective sheet in opticalproperties and durability, has satisfactory mechanical properties, andis more flexible and lighter than the glass sheet, excellent inworkability and easy to handle.

There is no possibility that the cyclic polyolefin film or sheet inaccordance with the present invention causes environmental destructionof pollution when disposed of after use.

The cyclic polyolefin resin film or sheet in accordance with the presentinvention may be, for example, any one of films or sheets of theforegoing cyclic polyolefin resins formed by a film forming process,such as an extrusion process, a casting process, a T-die extrusionprocess, a cutting process, an inflation process or the like, any one ofmultilayer films or multilayer sheets of two or more kinds of theforegoing cyclic polyolefin resins formed by a coextrusion process, orany one of films or sheets formed by subjecting a mixture of a pluralityof kinds of the foregoing cyclic polyolefin resins to a film formingprocess. When necessary, the cyclic polyolefin resin film or sheet maybe a uniaxially or biaxially oriented film or sheet formed by subjectinga cyclic polyolefin resin film or sheet to a uniaxial or biaxialorientation process of a tenter system or a tubular film system.

The thickness of the cyclic polyolefin resin film or sheet is in therange of about 12 to about 300 μm, desirably, in the range of about 25to about 200 μm.

It is desirable that the cyclic polyolefin resin film or sheet of thepresent invention has a visible light transmittance of 90% or above,preferably, 95% or above and a property to transmit all incidentsunlight and to absorb the same.

When forming the cyclic polyolefin resin film or sheet, variouscompounding ingredients and additives may be added to the cyclicpolyolefin resin to improve the workability, heat resistance, weatherresistance, strength, mechanical properties, dimensional stability,oxidation resistance, slipperiness, releasability, flame retardancy,antifungal property, electric properties, piercing strength and thelike. The amount of each of the compounding ingredients and theadditives is in the range of a very small percent to several tenspercent and may optionally be determined according to the purpose.

The cyclic olefin resin may contain commonly known additives, such as alubricant, a crosslinking agent, an oxidation inhibitor, an ultravioletabsorber, a light stabilizer, a filler, a reinforcing material,reinforcing fibers, an antistatic agent, a flame retarder, aflame-resistant agent, a foaming agent, an antifungus agent, a pigmentand the like. The cyclic polyolefin resin may further contain modifiers.

In the present invention, it is preferable to use a cyclic polyolefinresin film or sheet of a composite cyclic polyolefin resin; produced bypreparing a mixture of a cyclic polyolefin resin, an oxidationinhibitor, an ultraviolet absorber or one or a plurality of kinds ofreinforcing fibers, and kneading the mixture to improve the weatherresistance, strength, piercing strength and the like.

When necessary, a surface-treated layer 3 may be formed in a surface ofthe fluorocarbon resin sheet by a surface pretreatment process toimprove the adhesion between the surface of the cyclic polyolefin filmor sheet and the deposited inorganic oxide thin film.

The surface-treated layer 3 may be formed by, for example, a coronadischarge treatment, an ozone treatment, a low-temperature plasmatreatment using oxygen gas or nitrogen gas, a glow discharge treatment,an oxidation treatment using a chemical or the like. The surface-treatedlayer 3 may be a corona-treated layer, an ozone-treated layer, aplasma-treated layer, an oxidized layer or the like.

The surface pretreatment of the cyclic polyolefin resin film or sheet isa method of improving adhesion between the cyclic polyolefin resin filmor sheet and the deposited inorganic oxide thin film. The surface of thecyclic polyolefin resin film or sheet is finished by the surfacepretreatment to improve the adhesion between the cyclic polyolefin resinfilm or sheet and the deposited inorganic oxide thin film . Theimprovement of adhesion can be achieved by forming, instead of formingthe surface-treated layer, a layer of a primer, an undercoater, ananchoring agent, an adhesive or a deposited undercoating material.

Suitable materials for forming the coating layer are, for example,composite resins containing a polyester resin, a polyamide resin, apolyurethane resin, an epoxy resin, a phenolic resin, a (meta)acrylicresin, a polyvinyl acetate resin, a polyolefin resin such as apolyethylene, a polypropylene or a copolymer or a resin obtained bymodifying one of those resins, a cellulose resin or the like as aprincipal component of a vehicle.

In the present invention, the composite resin may contain an ultravioletabsorber and/or an oxidation inhibitor for weather resistanceimprovement.

The composite resin may contain one or a plurality of the foregoingultraviolet absorbers.

The composite resin may contain one or a plurality of the foregoingoxidation inhibitors.

The ultraviolet absorber and/or the oxidation inhibitor content isdependent on the shape and density of particles and a preferableultraviolet absorber and/or the oxidation inhibitor content is in therange of about 0.1 to about 10% by weight.

The coating layer may be formed of a coating material of, for example, asolvent type, an aqueous type or an emulsion type by a roller coatingprocess, a gravure coating process, a kiss-roll coating process or thelike. The coating layer may be formed by a coating process subsequent toa resin film or sheet forming process or a biaxial orientation process,or by an in-line coating process included in the film forming process orthe biaxial orientation process.

The surface-treated layer may be formed on one surface of the cyclicpolyolefin resin film or sheet to protect the cyclic polyolefin resinfilm or sheet from vapor deposition conditions for forming the depositedinorganic oxide thin film, to suppress yellowing, deterioration,shrinkage or cohesive failure in a surface layer or an inner layer ofthe cyclic polyolefin resin film or sheet, and to improve the adhesionbetween the cyclic polyolefin resin film or sheet and the depositedinorganic oxide thin film. The surface-treated layer , i.e., adeposition-resistant protective film, such as a deposited inorganicoxide thin film, may be formed by, for example, a chemical vapordeposition process (CVD process), such as a plasma chemical vapordeposition process, a thermal chemical vapor deposition process or aphotochemical vapor deposition process, or a physical vapor depositionprocess (PVD process), such as a vacuum evaporation process, asputtering process or an ion plating process.

The thickness of the deposition-resistant protective film of siliconoxide or the like may be less than 150 Å. The deposition-resistantprotective film may be a nonbarrier film not having any barrier effectto inhibit the permeation of moisture and oxygen gas. Concretely, thethickness of the deposition-resistant protective film is in the range ofabout 10 to about 100 Å, more preferably, in the range of about 20 to 80Å, more preferably, in the range of about 30 to about 60 Å.

If the thickness is greater than 150 Å, more concretely 100 Å, 80 Å or60 Å, the cyclic polyolefin resin film or sheet is exposed to severedeposition conditions. Consequently, the cyclic polyolefin resin film orsheet turns yellow, cohesive failure occurs, the formation of asatisfactory deposition-resistant protective film becomes difficult, andcracks develop in the film. If the thickness is less than 10 Å, 20 Å or30 Å, the film is incapable of functioning as an effectivedeposition-resistant protective film.

When the cyclic polyolefin resin film or sheet forms the outermost layerof a solar battery, the cyclic polyolefin resin film or sheet may be anembossed film or sheet having an embossed surface or embossed surfacesfinished by an embossing process to provide the cyclic polyolefin resinfilm or sheet with a sunlight diffusing effect or an antireflectioneffect.

The embossed surface may be such as having irregularities of sizes inthe range of a submicron size to several hundreds micrometer. Theirregularities may be of any suitable shape, such as a pyramidal shape,a V-shape or a plaid-shape.

The deposited inorganic oxide thin film may be formed by the continuousvacuum evaporation system shown in FIG. 8.

The low-temperature plasma chemical vapor deposition process for formingthe deposited inorganic oxide thin film may be carried out by thelow-temperature plasma chemical vapor deposition system shown in FIG. 9.

When fabricating a solar battery module, the reinforcing fibers may be,for example, glass fibers or filaments, carbon fibers or filaments,aramid fibers or filaments, polyamide fibers or filaments, polyesterfibers or filaments, natural fibers or the like. The reinforcing fibersor filaments, or a nonwoven fabric of the reinforcing fibers orfilaments may be used for forming a fiber-reinforcing layer.

It is also possible to form the fiber-reinforced layer by preparing amixture of the reinforcing fibers or filaments, such as the foregoingglass fibers or filaments, carbon fibers or filaments, aramid fibers orfilaments, polyamide fibers or filaments, polyester fibers or filaments,natural fibers or the like, or a nonwoven fabric or a sheet resembling anonwoven fabric of the reinforcing fibers or filaments, and a resin forforming the filler layer, such as one of fluorocarbon resins,ethylene-vinyl acetate resins, methacrylate copolymers, polyethyleneresins, polypropylene resins, modified polyolefin resins produced bymodifying polyolefin resins, such as polyethylene resins orpolypropylene resins, by an unsaturated carboxylic acid, such as acrylicacid, itaconic acid, maleic acid or fumaric acid, cyclic polyolefinresins, polyvinyl butyral resins, silicone resins, epoxy resins,(meta)acrylic resins and the like, kneading the mixture, and forming afilm of the kneaded mixture.

EXAMPLES Examples of the Second Embodiment will Concretely be DescribedHereinafter Example 1

(1) A roll of a 100 μm thick polydicyclopentadiene resin sheet, i.e.,base sheet, was mounted on a feed roll of a continuous vacuumevaporation system. The polydicyclopentadiene resin sheet was unwoundand wound around a coating drum and a 500 Å thick deposited aluminumoxide thin film was deposited on a treated surface of thepolydicyclopentadiene resin sheet treated for adhesion improvement by areactive vacuum evaporation process of an electron beam (EB) heatingsystem. Aluminum was used as an evaporation source and oxygen gas wassupplied to the continuous vacuum evaporation system.

Deposition Conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

EB power: 40 kW

Sheet moving speed: 600 m/min

(2) A protective sheet in accordance with the present invention for asolar battery module was completed by subjecting the 500 Å thickdeposited aluminum oxide thin film formed on the surface of thepolydicyclopentadiene resin sheet to a glow-discharge plasma process toform a plasma-processed surface. The glow-discharge plasma process wascarried out by a glow-discharge plasma producing apparatus of 1500 W inplasma output immediately after the deposition of the 500 Å thickdeposited aluminum oxide thin film. In the glow-discharge plasmaprocess, an oxygen/argon mixed gas of 19/1 in O₂/Ar ratio was suppliedso that the pressure of the oxygen/argon mixed gas is maintained at6×10⁻⁵ torr and the processing speed was 420 m/min.

(3) A solar battery module was fabricated by using the protective sheetthus fabricated. The protective sheet, a 400 μm thick ethylene-vinylacetate copolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film were superposedin that order with the plasma-processed deposited aluminum oxide thinfilm facing inside and the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadieneresin sheet was used instead of the 100 μm thick polydicyclopentadieneresin sheet as the base sheet.

Example 2

(1) A roll of a 100 μm thick polydicyclopentadiene resin sheet, i.e.,base sheet, was mounted on a feed roll of a plasma chemical vapordeposition system. A 500 Å thick deposited silicon oxide thin film wasdeposited on a treated surface of the polydicyclopentadiene resin sheettreated for adhesion improvement under the following conditions.

Deposition Conditions:

Reaction gas mixing ratio: Hexamethyldisiloxane/oxygen/helium=1/10/10(Unit: slm)

Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

Vacuum in deposition chamber: 6.0×10⁻² mbar

Power supplied to cooling electrode drum: 20 kW

Film moving speed: 80 m/min

Surface for vapor deposition: Corona-processed surface

(2) A protective sheet in accordance with the present invention for asolar battery module was completed by subjecting the 500 Å thickdeposited silicon oxide thin film formed on the surface of thepolydicyclopentadiene resin sheet to a corona discharge process to forma corona-processed surface and to increase the surface tension of thedeposited silicon oxide thin film from 35 dyne to 60 dyne. Coronadischarge power was 10 kW and the sheet was moved at a moving speed of100 m/min.

(3) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the corona-processed deposited silicon oxide thin film facinginside and the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that 100 μm thick polycyclopentadieneresin sheet was used instead of the 100 μm thick polydicyclopentadieneresin sheet.

Example 3

(1) A roll of a 300 μm thick polydicyclopentadiene resin sheetcontaining an ultraviolet absorber was mounted on a feed roll of aplasma chemical vapor deposition system. A 500 Å thick deposited siliconoxide thin film was deposited on a treated surface of thepolydicyclopentadiene resin sheet treated for adhesion improvement underthe following conditions.

Deposition Conditions:

Reaction gas mixing ratio: Hexamethyldisiloxane/oxygen/helium=1/10/10(Unit: slm)

Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

Vacuum in deposition chamber: 6.0×10⁻² mbar

Power supplied to cooling electrode drum: 20 kW

Film moving speed: 80 m/min

Surface for deposition: Corona-processed surface

The surface of the 500 Å thick deposited silicon oxide thin film formedon the polydicyclopentadiene resin sheet was subjected to a coronadischarge process to form a corona-processed surface and to increase thesurface tension of the deposited silicon oxide thin film from 35 dyne to60 dyne. Corona discharge power was 10 kW and the sheet was moved at amoving speed of 100 m/min.

(2) A roll of the polydicyclopentadiene resin sheet provided with thecorona-processed deposited silicon oxide thin film was mounted on a feedroll of a continuous vacuum evaporation system. Thepolydicyclopentadiene resin sheet was unwound and wound around a coatingdrum and a 500 Å thick deposited aluminum oxide thin film was depositedon the corona-processed surface of the deposited silicon oxide thin filmformed on the polydicyclopentadiene resin sheet by a reactive vacuumevaporation process of an electron beam (EB) heating system. Aluminumwas used as an evaporation source and oxygen gas was supplied to thecontinuous vacuum evaporation system.

Deposition Conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

EB power: 40 kW

Film moving speed: 600 m/min

A protective sheet in accordance with the present invention for a solarbattery module was completed by subjecting the 500 Å thick depositedaluminum oxide thin film formed on the surface of thepolydicyclopentadiene resin sheet to a glow-discharge plasma process toform a plasma-processed surface. The glow-discharge plasma process wascarried out by a glow-discharge plasma producing apparatus of 1500 W inplasma output immediately after the deposition of the 500 Å thickdeposited aluminum oxide thin film. In the glow-discharge plasmaprocess, an oxygen/argon mixed gas of 19/1 in O₂/Ar ratio was suppliedso that the pressure of the oxygen/argon mixed gas is maintained at6×10⁻⁵ torr and the processing speed was 420 m/min.

(3) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The protectivesheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μmthick biaxially oriented polyethylene terephthalate film provided withan array of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and a 50 μm thick biaxially orientedpolyethylene terephthalate film were superposed in that order with theplasma-processed deposited aluminum oxide thin film facing inside andthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the front surfaceprotective sheet. Those component layers were laminated by usingadhesive layers of an acrylic resin to complete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 300 μm thick polycyclopentadieneresin sheet containing an ultraviolet absorber was used instead of the300 μm thick polydicyclopentadiene resin sheet containing an ultravioletabsorber and used as the base sheet.

Example 4

(1) Protective sheets that are the same as the protective sheet inExample 1 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the plasma-processed deposited aluminum oxide thin films ofthe front surface and the back surface protective sheet facing insideand with the surface of the 38 μm thick polyethylene terephthalate filmprovided with the solar cells facing the front surface protective sheet,and laminating those component layers by using adhesive layers of anacrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 100 μm thick polycyclopentadiene resinsheets were used instead of the 100 μm thick polydicyclopentadiene resinsheets.

Example 5

(1) Protective sheets that are the same as the protective sheet inExample 2 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the plasma-processed deposited silicon oxide thin films ofthe front surface and the back surface protective sheet facing insideand with the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 100 μm thick polycyclopentadiene resinsheets were used instead of the 100 μm thick polydicyclopentadiene resinsheets.

Example 6

(1) Protective sheets that are the same as the protective sheet inExample 3 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the plasma-processed deposited aluminum oxide thin films ofthe front surface and the back surface protective sheet facing insideand with the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 300 μm thick polycyclopentadiene resinsheets containing an ultraviolet absorber were used instead of the 300μm thick polydicyclopentadiene resin sheet containing the ultravioletabsorber.

Example 7

(1) A protective sheet that is the same as the protective sheet inExample 1 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a3 mm thick glass sheet, a 400 μm thick ethylene-vinyl acetate copolymersheet, a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the plasma-processed deposited aluminum oxidethin film of the back surface protective sheet facing inside and withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the 3 mm thickglass sheet, and laminating those component layers by using adhesivelayers of an acrylic resin.

(2) A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 100 μm thick polycyclopentadiene resinsheet was used instead of the 100 μm thick polydicyclopentadiene resinsheet.

Example 8

(1) A protective sheet that is the same as the protective sheet inExample 2 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with thecorona-processed deposited silicon oxide thin film of the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick polyvinyl fluoride sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

(2) A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 100 μm thick polycyclopentadiene resinsheet was used instead of the 100 μm thick polydicyclopentadiene resinsheet.

Example 9

(1) A protective sheet that is the same as the protective sheet inExample 3 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with theplasma-processed deposited aluminum oxide thin film of the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick polyvinyl fluoride sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

(2) A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 100 μm thick polycyclopentadiene resinsheet was used instead of the 100 μm thick polydicyclopentadiene resinsheet.

Example 10

(1) A roll of a 100 μm thick polydicyclopentadiene resin sheetcontaining an ultraviolet absorber comprising ultrafine titanium oxidepowder, and glass fibers was mounted on a feed roll of a plasma chemicalvapor deposition system. A 50 Å thick deposited silicon oxide thin filmas a deposition-resistant protective film was deposited on a surface ofthe polydicyclopentadiene resin sheet under the following conditions.

Deposition Conditions:

Reaction gas mixing ratio: Hexamethyldisiloxane/oxygen/helium=5/5/5(Unit: slm)

Vacuum in vacuum chamber: 7.0×10⁻⁶ mbar

Vacuum in deposition chamber: 3.8×10⁻² mbar

Power supplied to cooling electrode drum: 15 kW

Sheet moving speed: 100 m/min

(2) A roll of the polydicyclopentadiene resin sheet 35 provided with thedeposition-resistant protective film was mounted on a feed roll of aplasma chemical vapor deposition system. A 800 Å thick deposited siliconoxide thin film was deposited on the deposition-resistant protectivefilm formed on the polydicyclopentadiene resin sheet.

Deposition Conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

Vacuum in deposition chamber: 6.0×10⁻² mbar

Power supplied to cooling electrode drum: 20 kw

Film moving speed: 80 m/min

A protective sheet in accordance with the present invention for a solarbattery module was completed by subjecting the 800 Å thick depositedsilicon oxide thin film to a corona discharge process to form acorona-processed surface and to increase the surface tension of thedeposited silicon oxide thin film from 35 dyne to 60 dyne. Coronadischarge power was 10 kW and the sheet was moved at a moving speed of100 m/min.

(3) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The protectivesheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μmthick biaxially oriented polyethylene terephthalate film provided withan array of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and a 50 μm thick biaxially orientedpolyethylene terephthalate film were superposed in that order with thecorona-processed deposited silicon oxide thin film facing inside and thesurface of the 38 μm thick polyethylene terephthalate film provided withthe array of amorphous silicon solar cells facing the front surfaceprotective sheet. Those component layers were laminated by usingadhesive layers of an acrylic resin to complete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadieneresin sheet containing an ultraviolet absorber comprising ultrafinetitanium oxide powder, and glass fibers was used instead of the 100 μmthick polydicyclopentadiene resin sheet containing an ultravioletabsorber comprising ultrafine titanium oxide powder, and glass fiber.

Example 11

(1) A roll of the polydicyclopentadiene resin sheet in Example 10provided with the deposition-resistant protective film was mounted on afeed roll of a continuous vacuum evaporation system. Thepolydicyclopentadiene resin sheet was unwound and wound around a coatingdrum and a 800 Å thick deposited aluminum oxide thin film was depositedon the deposition-resistant protective film by a reactive vacuumevaporation process of an electron beam (EB) heating system. Aluminumwas used as an evaporation source and oxygen gas was supplied to thecontinuous vacuum evaporation system.

Deposition Conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

EB power: 40 kW

Film moving speed: 600 m/min

A protective sheet in accordance with the present invention for a solarbattery module was completed by subjecting the 800 Å thick depositedaluminum oxide thin film to a glow-discharge plasma process to form aplasma-processed surface. The glow-discharge plasma process was carriedout by a glow-discharge plasma producing apparatus of 1500 W in plasmaoutput immediately after the deposition of the 800 Å thick depositedaluminum oxide thin film. In the glow-discharge plasma process, anoxygen/argon mixed gas of 19/1 in O₂/Ar ratio was supplied so that thepressure of the oxygen/argon mixed gas is maintained at 6×10⁻⁵ torr andthe processing speed was 420 m/min.

(2) The protective sheet thus fabricated was used as a front surfaceprotective sheet. A 400 μm thick ethylene-vinyl acetate copolymer sheetwas laminated to the plasma-processed surface of the deposited aluminumoxide thin film with an adhesive layer of an acrylic resin.

A 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderon the ethylene-vinyl acetate copolymer sheet laminated to theprotective sheet with the he surface of the 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet.Those component layers were laminated by using adhesive layers of anacrylic resin to complete a solar battery module.

(3) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadieneresin sheet containing an ultraviolet absorber comprising ultrafinetitanium oxide powder, and glass fibers was used instead of the 100 μmthick polydicyclopentadiene resin sheet containing an ultravioletabsorber comprising ultrafine titanium oxide powder, and glass fibers.

Example 12

(1) A 100 μm thick polydicyclopentadiene resin sheet containing anultraviolet absorber comprising ultrafine titanium oxide powder, andglass fibers was used. One of the surfaces of the polydicyclopentadieneresin sheet was processed by an embossing process using an embossingroller to form an embossed surface provided with pyramidal projectionsof 1 μm in size.

A roll of the polydicyclopentadiene resin sheet having the embossedsurface was mounted on a feed roll of a continuous vacuum evaporationsystem. The polydicyclopentadiene resin sheet was unwound and woundaround a coating drum and a 50 Å thick deposited aluminum oxide thinfilm as a deposition-resistant protective film was deposited on theother surface not embossed of the polydicyclopentadiene resin sheet by areactive vacuum evaporation process of an electron beam (EB) heatingsystem. Aluminum was used as an evaporation source and oxygen gas wassupplied to the continuous vacuum evaporation system.

Deposition Conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

EB power: 20 kW

Film moving speed: 500 m/min

(2) A protective sheet in accordance with the present invention for asolar battery module was completed by forming a 800 Å thick depositedaluminum oxide thin film on the deposition-resistant protective filmformed on the unembossed surface of the polydicyclopentadiene resinsheet by a reactive vacuum evaporation process of an electron beam (EB)heating system similar to that that in Example 1, and subjecting the 800Å thick deposited aluminum oxide thin film to a plasma process to form aplasma-processed surface.

(3) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The protectivesheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μmthick biaxially oriented polyethylene terephthalate film provided withan array of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and a 50 μm thick biaxially orientedpolyethylene terephthalate film were superposed in that order with theplasma-processed surface of the deposited aluminum oxide thin filmfacing inside and the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadieneresin sheet containing an ultraviolet absorber comprising ultrafinetitanium oxide powder, and glass fibers and having an embossed surfacewas used instead of the 100 μm thick polydicyclopentadiene resin sheetcontaining an ultraviolet absorber comprising ultrafine titanium oxidepowder, and glass fibers and having the embossed surface.

Example 13

(1) Protective sheets that are the same as the protective sheet inExample 10 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the corona-processed deposited silicon oxide thin films ofthe front surface and the back surface protective sheet facing insideand with the surface of the 38 μm thick polyethylene terephthalate filmprovided with the solar cells facing the front surface protective sheet,and laminating those component layers by using adhesive layers of anacrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 100 μm thick polycyclopentadiene resinsheets containing an ultraviolet absorber comprising ultrafine titaniumoxide powder, and glass fibers were used instead of the 100 μm thickpolydicyclopentadiene resin sheets containing an ultraviolet absorbercomprising ultrafine titanium oxide powder, and glass fibers face.

Example 14

(1) Protective sheets that are the same as the protective sheet inExample 11 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. A 400 μm thickethylene-vinyl acetate copolymer sheet was laminated to theplasma-processed surface of the deposited aluminum oxide thin film ofthe front surface protective sheet with an adhesive layer of an acrylicresin to form a first laminated structure.

A 400 μm thick ethylene-vinyl acetate copolymer sheet was laminated tothe plasma-processed surface of the deposited aluminum oxide thin filmof the back surface protective sheet with an adhesive layer of anacrylic resin to form a second laminated structure.

A 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells was sandwichedbetween the first and the second laminated structure with the 400 μmthick ethylene-vinyl acetate copolymer sheets contiguous with the 38 μmthick biaxially oriented polyethylene terephthalate film and with thesurface of the 38 μm thick biaxially oriented polyethylene terephthalatefilm facing the front surface protective sheet.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 100 μm thick polycyclopentadiene resinsheets containing an ultraviolet absorber comprising ultrafine titaniumoxide powder, and glass fibers were used instead of the 100 μm thickpolydicyclopentadiene resin sheets containing an ultraviolet absorbercomprising ultrafine titanium oxide powder, and glass fibers face.

Example 15

(1) Protective sheets that are the same as the protective sheet inExample 12 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the plasma-processed deposited aluminum oxide thin films ofthe front surface and the back surface protective sheet facing insideand with the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 100 μm thick embossedpolycyclopentadiene resin sheets containing an ultraviolet absorbercomprising ultrafine titanium oxide powder, and glass fibers were usedinstead of the 100 μm thick embossed polydicyclopentadiene resin sheetscontaining the ultraviolet absorber comprising ultrafine titanium oxidepowder, and glass fibers.

Example 16

(1) A protective sheet that is the same as the protective sheet inExample 10 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a3 mm thick glass sheet, a 400 μm thick ethylene-vinyl acetate copolymersheet, a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the corona-processed deposited silicon oxidethin film of the back surface protective sheet facing inside and withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the 3 mm thickglass sheet, and laminating those component layers by using adhesivelayers of an acrylic resin.

(2) A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 100 μm thick polycyclopentadiene resinsheet containing an ultraviolet absorber comprising ultrafine titaniumoxide powder, and glass fibers was used instead of the 100 μm thickpolydicyclopentadiene resin sheet containing an ultraviolet absorbercomprising ultrafine titanium oxide powder, and glass fibers.

Example 17

(1) A protective sheet that is the same as the protective sheet inExample 11 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with theplasma-processed deposited aluminum oxide thin film of the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick polyvinyl fluoride sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

(2) A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 100 μm thick polycyclopentadiene resinsheet containing an ultraviolet absorber comprising ultrafine titaniumoxide powder, and glass fibers was used instead of the 100 μm thickpolydicyclopentadiene resin sheet containing an ultraviolet absorbercomprising ultrafine titanium oxide powder, and glass fibers.

Example 18

(1) A protective sheet that is the same as the protective sheet inExample 11 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with theplasma-processed deposited aluminum oxide thin film of the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the 50 μm thick polyvinyl fluoride sheet, andlaminating those component layers by using adhesive layers of an acrylicresin. (2) A protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick embossedpolycyclopentadiene resin sheet containing an ultraviolet absorbercomprising ultrafine titanium oxide powder, and glass fibers was usedinstead of the 100 μm thick embossed polydicyclopentadiene resin sheetcontaining an ultraviolet absorber comprising ultrafine titanium oxidepowder, and glass fibers.

COMPARATIVE EXAMPLE 1

A 3 mm thick glass sheet was used as a base sheet for a front surfaceprotective sheet for a solar battery module. The solar battery modulewas fabricated by superposing the 3 mm thick glass sheet, a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and a 50 μm thick biaxially oriented polyethylene terephthalatefilm in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the glass sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

COMPARATIVE EXAMPLE 2

A 50 μm thick polyvinyl fluoride sheet (PVF sheet) was used as a basesheet for a front surface protective sheet for a solar battery module.The solar battery module was fabricated by superposing the 50 μm thickpolyvinyl fluoride sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film in that orderwith the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing the 50μm thick polyvinyl fluoride sheet, and laminating those component layersby using adhesive layers of an acrylic resin.

COMPARATIVE EXAMPLE 3

Two 50 μm thick polyvinyl fluoride sheets (PVF sheets) were used as basesheets for a front surface protective sheet and a back surfaceprotective sheet for a solar battery module. The solar battery modulewas fabricated by superposing one of the two 50 μm thick polyvinylfluoride sheets (PVF sheets), a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and theother 50 μm thick polyvinyl fluoride sheet (PVF sheet) in that orderwith the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing the 50μm thick polyvinyl fluoride sheet serving as the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

Experiments

The protective sheets in Examples 1 to 18 and in Comparative examples 1to 3 were subjected to total transmittance measurement. The solarbattery modules in Examples 1 to 18 and Comparative examples 1 to 3 weresubjected to solar battery module evaluation tests.

(1) Total Transmittance Measurement

Total transmittance (%) of each of the protective sheets in Examples 1to 18 and Comparative examples 1 to 3 against the total transmittance ofthe base sheet as a reference total transmittance was measured by acolor computer.

(2) Solar Battery Module Evaluation Tests

The solar battery modules were subjected to environmental tests inconformity to conditions specified in JIS C8917-1989. Photovoltaicoutput of the solar battery modules was measured before and afterenvironmental tests.

(3) Moisture Permeability and oxygen Permeability

The moisture permeabilities of the protective sheets in Examples 1 to 18and Comparative examples 1 to 3 were measured in an atmosphere of 40° C.and 90% RH by a moisture permeability measuring apparatus (PERMATRAN,MOCON, USA). The oxygen permeabilities of the protective sheets inExamples 1 to 18 and Comparative examples 1 to 3 were measured in anatmosphere of 23° C. and 90% RH by an oxygen permeability measuringapparatus (OXTRAN, MOCON, USA). Measured data is tabulated in Table 2-1.

TABLE 2-1 Total Moisture oxygen Output trans- permea- permea- reductionmittance bility bility ratio (%) (g/m²/24 hr) (cc/m²/24 hr/atm) (%)Example 1 92 0.5 5.3 4 Example 2 91 0.2 2.0 3 Example 3 91 0.1 1.1 2Example 4 92 0.5 4.9 2 Example 5 91 0.2 1.8 2 Example 6 91 0.1 1.0 1Example 7 92 0.5 5.1 3 Example 8 91 0.2 2.1 4 Example 9 91 0.1 1.1 4Example 10 90 0.3 4.5 3 Example 11 90 0.2 2.0 3 Example 12 90 0.1 0.9 2Example 13 90 0.3 3.9 2 Example 14 89 0.2 1.5 2 Example 15 91 0.3 0.8 1Example 16 90 0.2 0.7 1 Example 17 90 0.1 0.6 1 Example 18 89 0.1 0.9 1Comparative 89 15.5 40.3 14 Example 1 Comparative 93 26.3 27.7 15Example 2 Comparative 93 26.3 27.7 12 Example 3

In table 2-1, total transmittance is expressed in a unit of %, moisturepermeability is expressed in a unit of g/m²/day·40° C.·100% RH, oxygenpermeability is expressed in a unit of cc/m²/day·23° C.·90% RH, andoutput reduction ratio is expressed in a unit of %.

As obvious from Table 2-1, the protective sheets in Examples 1 to 18have high total transmittances, respectively, and are excellent inmoisture impermeability and oxygen impermeability.

The output reduction ratios of the solar battery modules employing theprotective sheets in Examples 1 to 18 were low.

The protective sheets in Comparative examples 1 to 3 had high totaltransmittances, respectively. However, the moisture impermeabilities andthe oxygen impermeabilities of the protective sheets in Comparativeexamples 1 to 3 were low. Consequently, the output reduction ratios ofthe solar battery modules employing the protective sheets in Comparativeexamples 1 to 3 were high.

As apparent from the foregoing description, the present invention uses acyclic polyolefin resin film or sheet as a base sheet, fabricates aprotective sheet for a solar battery module by forming a transparent,vitreous deposited inorganic oxide thin film, such as a silicon oxidethin film or an aluminum oxide thin film, on one of the surfaces of thecyclic polyolefin resin film or sheet; the protective sheet thusfabricated is used as the front surface protective sheet or the backsurface protective sheet of a solar battery module; the solar batterymodule is fabricated by, for example, superposing the protective sheetas a front surface protective sheet, a filler layer, a film providedwith solar cells, i.e., photovoltaic cells, a filler layer and a backsurface protective sheet for a solar battery module in that order in asuperposed structure with the deposited inorganic oxide thin film facinginside, bringing the component layers of the superposed structure intoclose contact by vacuum and bonding together those component layers by alamination process using hot pressing; and the protective sheet isexcellent in sunlight transmittance, strength, weather resistance, heatresistance, water resistance, light resistance, wind endurance,hailstorm resistance, chemical resistance, moisture resistance, soilresistance and piercing strength, has a high impermeability to moistureand oxygen, limits performance degradation due to aging to the leastextent, very durable, has excellent protective ability, and can be usedfor the stable fabrication of a low-cost, safe solar battery module.

The materials mentioned in the description of the first embodiment areapplicable to the second embodiment.

THIRD EMBODIMENT

The present invention will be described hereinafter with reference tothe accompanying drawings.

In this description, the term “sheet” is used in its broad sense todenote both sheets and films, and the term “film” is used in its broadsense to denote both sheets and films.

Protective sheets in accordance with the present invention for solarbattery modules and solar battery modules employing the protectivesheets will be described with reference to the accompanying drawings.FIGS. 10, 11 and 12 are typical sectional views of protective sheets inexamples in a third embodiment according to the present invention for asolar battery module, and FIGS. 13, 14 and 15 are typical sectionalviews of solar battery modules employing the protective sheet shown inFIG. 10.

Referring to FIG. 10, a protective sheet A embodying the presentinvention for a solar battery module has a basic structure comprising aplastic sheet (weather-resistant sheet) 1, a deposited inorganic oxidefilm 2 formed on one of the surfaces of the plastic sheet 1, and acoating film 103 of a condensation polymer produced through thehydrolysis of a silicon compound and formed on the deposited inorganicoxide film 2.

As shown in FIG. 11, a protective sheet A₁ in an example of the thirdembodiment for a solar battery module comprises a plastic sheet 1, amultilayer film 4 consisting of at least two deposited inorganic oxidefilms 2 and formed on one of the surfaces of the plastic sheet 1, and acoating film 103 of a condensation polymer produced through thehydrolysis of a silicon compound and formed on the deposited inorganicoxide film 2 of the multilayer film 4.

As shown in FIG. 12 a protective sheet A₃ in a third example of thethird embodiment for a solar battery module comprises a plastic sheet 1,a composite film 5 consisting of a first deposited inorganic oxide film2 a formed on one of the surfaces of the plastic sheet 1 by a chemicalvapor deposition process and a deposited inorganic oxide film 2 b formedon the deposited inorganic oxide film 2 a by a physical vapor depositionprocess, and formed on one of the surfaces of the plastic film 1, and acoating film 13 of a condensation polymer produced through thehydrolysis of a silicon compound and formed on the deposited inorganicoxide film.

Those protective sheets are only examples of the protective sheet in thefirst embodiment and the present invention is not limited thereto.

For example, in the protective sheet A₂ shown in FIG. 12, a depositedinorganic oxide film may be formed first on the surface of the plasticsheet 1 by a physical vapor deposition process, and then anotherdeposited inorganic oxide film may be formed by a chemical vapordeposition process.

A solar battery module employing this protective sheet A embodying thepresent invention and shown in FIG. 10 will be described by way ofexample. Referring to FIG. 13, a solar battery module T employs theprotective sheet A shown in FIG. 10 as its front surface protectivesheet 11. The solar battery module T is fabricated by superposing thefront surface protective sheet 11(A), a filler layer 12, a photovoltaiclayer 13 of solar cells, a filler layer 14 and a generally known backsurface protective sheet 15 in that order in a superposed structure, andsubjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing. The coating film 103 of the frontsurface protective sheet 11 faces inside.

Another solar battery module T₁ shown in FIG. 14 employs the protectivesheet A shown in FIG. 1 as its back surface protective sheet 16. Thesolar battery module T₁ is fabricated by superposing a generally knownfront surface protective sheet 17, a filler layer 12, a photovoltaiclayer 13 of solar cells, a filler layer 14 and the back surfaceprotective sheet 16(A) in that order in a superposed structure, andsubjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing. The coating film 103 of theprotective sheet 16 faces inside.

A third solar battery module T₂ shown in FIG. 15 employs the protectivesheet A shown in FIG. 10 as its front surface protective sheet 11 andits back surface protective sheet 16. The solar battery module T₂ isfabricated by superposing the front surface protective sheet 11(A), afiller layer 12, a photovoltaic layer 13 of solar cells, a filler layer14 and the protective sheet 16(A) in that order in a superposedstructure, and subjecting the superposed structure to a generally knownforming process, such as a lamination process, in which those componentlayers of the superposed structure are brought into close contact byvacuum and are bonded together by hot pressing. The coating film 103 ofeach of the protective sheets 11 and 16 faces inside.

The foregoing protective sheets in accordance with the present inventionand the foregoing solar battery modules employing those protectivesheets are examples intended to illustrate the invention and not to beconstrued to limit the scope of the invention.

For example, the protective sheets shown in FIGS. 11 and 12 can beapplied to solar battery modules of various types. The foregoing solarbattery modules may comprise additional layers for sunlight absorption,reinforcement or the like. Basically, the plastic sheet(weather-resistant sheet) 1 for forming the protective sheet inaccordance with the present invention and the solar battery module maybe a film or sheet capable of withstanding deposition conditions forforming the deposited inorganic oxide film or coating conditions forforming the coating film, excellent in adhesion to the depositedinorganic oxide film or the coating film, capable of satisfactorilyholding the film without adversely affecting the characteristics ofthose films, excellent in sunlight transmittance that affect theabsorption of sunlight by a solar battery and the photovoltaic powergeneration of a solar battery, excellent in strength, weatherresistance, heat resistance, water resistance, light resistance, windendurance, hailstorm resistance and chemical resistance, having a highimpermeability to moisture and oxygen, limiting performance degradationto the least extent, very durable, and having excellent protectiveability. Those resin films or sheets may be those of, for example,polyethylene resins, polypropylene resins, cyclic polyolefin resins,polystyrene resins, acrylonitrile-styrene copolymers (AS resins),acrylonitrile-butadiene-styrene copolymers (ABS resins), polyvinylchloride resins, fluorocarbon resins poly(meta)acrylic resins,polycarbonate resins, polyester resins, such as polyethyleneterephthalate and polyethylene naphthalate, polyamide resins, such asnylons, polyimide resins, polyamidimide resins, polyaryl phthalateresins, silicone resins, polysulfone resins, polyphenylene sulfideresins, polyester sulfone resins, polyurethane resins, acetal resins,cellulose resins and the like.

Sheets of fluorocarbon resins, cyclic polyolefin resins, polycarbonateresins, poly(meta)acrylic resins and polyester resins are particularlypreferable.

According to the present invention, it is particularly preferable to usetransparent films or sheets of, for example, polytetrafluoroethylene(PTFE), perfluoroalcoxy resins (PFA), i.e., copolymers oftetrafluoroethylene and perfluoroalkylvinyl ether, copolymers oftetrafluoroethylene and hexafluoropropylene (FEP), copolymers oftetrafluoroethylene, perfluoroalkylvinyl ether and hexafluoropropylene(EPE), copolymers of tetrafluoroethylene and ethylene or propylene(ETFE), polychlorotrifluoroethylene resins (PCTFE) copolymers ofethylene and chlorotrifluoroethylene (ECTFE), vinylidene fluoride resins(PVDF), and one or some of fluorocarbon resins, such as vinyl fluorideresins (PVF).

Among those fluorocarbon resin sheets, sheets of polyvinyl fluorideresins (PVF) or copolymers of tetrafluoroethylene and ethylene orpropylene (ETFE) are particularly preferable from the view point oftransparency and sunlight transmittance.

According to the present invention, it is particularly preferable to usecyclic polyolefin resin sheets of, for example, cyclopentadiene and itsderivatives, dicyclopentadiene and its derivatives, cyclohexadiene andits derivatives, norbornadiene and its derivatives, polymers of cyclicdiene monomers, and copolymers of cyclic diene monomers and one or someof propylene, 4-methyl-1-pentene, styrene, butadiene, isoprene andolefin monomers.

According to the present invention, it is particularly preferable touse, among the foregoing transparent cyclic polyolefin resin sheets,transparent cyclic polyolefin sheets of cyclopentadiene and itsderivatives, dicyclopentadiene and its derivatives or polymers orcopolymers of cyclic diene monomers, such as norbornadiene and itsderivatives, because those sheets are excellent in weather resistanceand water resistance, are highly transparent and have high sunlighttransmittance.

The protective sheets of the solar battery modules using thefluorocarbon resin sheet or the cyclic polyolefin resin sheet utilizethe excellent properties of the fluorocarbon resin sheet or the cyclicpolyolefin resin sheet including mechanical properties, chemicalproperties and optical properties, more concretely, weather resistance,heat resistance, water resistance, light resistance, moistureresistance, soil resistance, chemical resistance and the like. Theprotective sheet is equal in optical properties, durability andprotective ability to a glass sheet commonly used as a protective sheet,has satisfactory mechanical properties including flexibility, andchemical properties, and is lighter than the glass sheet, excellent inworkability and easy to handle.

According to the present invention, the resin films or sheets may beformed of, for example, one or some of the foregoing resins by a filmforming process, such as an extrusion process, a casting process, aT-die extrusion process, a cutting process, an inflation process or thelike, may be multilayer films or sheets of two or more kinds of theforegoing resins formed by a coextrusion process, or may be films orsheets formed by subjecting a mixture of a plurality of kinds of theforegoing resins to a film forming process. When necessary, the resinfilms or sheets may be uniaxially or biaxially oriented films or sheetsformed by subjecting resin films or sheets to a uniaxial or biaxialorientation process of a tenter system or a tubular film system.

The thickness of the resin films or sheets is in the range of about 12to about 300 μm, preferably, in the range of about 20 to about 200 μm.

It is desirable that the resin films or sheets of the present inventionhave a visible light transmittance of 90% or above, preferably, 95% orabove and a property to transmit all incident sunlight and to absorb thesame.

When forming the resin films each of one or a plurality of the resins,various compounding ingredients and additives may be added to the resinor resins to improve the workability, heat resistance, weatherresistance, mechanical properties, dimensional stability, oxidationresistance, slipperiness, releasability, flame retardancy, antifungalproperty, electric properties and the like. The amount of each of thecompounding ingredients and the additives is in the range of a verysmall percent to several tens percent and may optionally be determinedaccording to the purpose.

The resins may contain commonly known additives, such as a lubricant, acrosslinking agent, an oxidation inhibitor, an ultraviolet absorber, alight stabilizer, a filler, a reinforcing material, a stiffener, anantistatic agent, a flame retarder, a flame-resistant agent, a foamingagent, an antifungus agent, a pigment and the like. The resins mayfurther contain modifiers.

When necessary, a surface-treated layer 3 (FIG. 10) may be formed in asurface of each of the resin films or sheets before forming a depositedinorganic oxide film on the surface to improve adhesion between theresin films or sheets and a deposited inorganic oxide film.

According to the present invention, the composite resins may contain,for example, an ultraviolet absorber and/or an oxidation inhibitor toimprove the light resistance and the like. may contain, for example, anultraviolet absorber and/or an oxidation inhibitor to improve the lightresistance and the like.

Description will be given of the coating film of a condensation polymerproduced through the hydrolysis of a silicon compound, employed in theprotective sheet in accordance with the present invention for a solarbattery module and a solar battery module. When forming the coatingfilm, a material containing a silicon compound as a principal componentor a solution of the material prepared by dissolving the material in anappropriate solvent, such as ethanol or isopropanol, is brought intocontact with a stoichiometrically necessary amount of water or an amountof water greater by one or several parts than the stoichiometricallynecessary amount for hydrolysis to prepare a condensation polymer.

Preferably, the hydrolysis is carried out at a temperature in the rangeof −20 to 130° C., more preferably, in the range of 0 to 30° C. or at atemperature corresponding to the boiling point of the selectively usedsolvent.

The most proper method of bringing the material into contact with wateris dependent particularly on the reactivity of the material.

The solution of the material may be dropped at long intervals into asurplus amount of water or the necessary amount of water may be added ata time or in a series of times to the solution prepared by selectivelydissolving the material.

It is advantageous to introduce water into the reactive mixture by meansof an organic or an inorganic solvent containing water instead of addingwater to the reactive mixture.

It is known that the introduction of water into the reactive using amolecular sieve, and an organic solvent containing water, such as 30%ethanol, is particularly proper for most cases.

Water can be added to the reactive mixture by using a reaction thatproduces water, such as a reaction for producing an ester from an acidand an alcohol.

Suitable materials as the solvent, in addition to the effective loweraliphatic alcohols, are ketones, preferably, lower dialkyl ketones, suchas acetone, and methyl isobutyl ketone, esters, preferably, lowerdialkyl ethers, such as diethyl ether, tetrahydrofuran (THF), amides,esters including ethyl acetate, dimethyl formamide and mixtures of thesame.

Condensation polymerization by hydrolysis may selectively using acatalyst, such as a compound that discharges protons or hydroxyl ions,or an amine.

Suitable materials as the catalyst are organic or inorganic acids, suchas hydrochloric acid and acetic acid, ammonia, alkaline metal andalkaline earth hydroxides, such as organic or inorganic salts includingsodium hydroxide, potassium hydroxide and calcium hydroxide, and aminessoluble in a reactive medium, such as lower alkylamines and alkanolamines.

Volatile acids and bases, such as ammonia and triethylamine, areparticularly preferable.

The concentration of the catalyst may be 3 mol per liter at thegreatest.

A mixture of all the source compounds need not necessarily be preparedbefore starting hydrolysis (condensation polymerization). Actually, in aspecific case, it is advantageous to bring some of the source compoundsinto contact with water in an initial stage of hydrolysis, and then tobring the rest later into contact with water.

To reduce precipitation to the least possible extent, it is preferableto add water in several steps, for example, in three steps.

In the first step, 1/10 to 1/20 of the amount of waterstoichiometrically necessary for hydrolysis is added to the sourcematerial.

After stirring a mixture of the source materials and water for a shorttime, 1/5 to 1/10 of the amount of water stoichiometrically necessaryfor hydrolysis is added to the mixture, the mixture is stirred for asort time, and an amount of water is added to the mixture so that thetotal amount of water added to the source material is a little greaterthan the stoichiometric amount.

Time necessary for condensation polymerization by hydrolysis isdependent on the source materials, the concentrations of the sourcematerials, the catalyst, reaction temperature and the like.

Generally, the reaction process for condensation polymerization byhydrolysis is conducted at atmospheric pressure. The reaction processmay be conducted at a higher-than-atmospheric pressure or at a reducedpressure.

After all the predetermined amount of water has been added to the sourcematerials, it is preferable to prepare a composite material comprising acondensation polymer produced through the hydrolysis of a siliconcompound, by stirring the mixture for a long time in the range of two tothree hours at room temperature or at a temperature slightly higher thanroom temperature.

According to the present invention, the composite material thus preparedis applied to or printed on the surface of the deposited inorganic oxidefilm in a composite material film, the composite material film is driedand aged to form the coating film. The composite material film may beformed by any one of coating processes including a floating-knifecoating process, a knife-over-roll coating process, an inverted knifecoating process, a squeeze roll coating process, a reverse roll coatingprocess, a roll coating process, a gravure roll coating process, akiss-roll coating process, an air blade coating process, a dip coatingprocess, a flow coating process, a spin coating process, a spray coatingprocess, a bar coating process, a curtain-flow coating process and thelike, or any one of printing processes including a gravure printingprocess, an offset printing process, a silk-screen printing process, atransfer printing process and the like.

The desirable thickness of the coating film as dried is in the range of0.2 to 50 g/m², more preferably, in the range of 1.0 to 25 g/m².

When curing the coating film of the composite material comprising thecondensation polymer produced through the hydrolysis of silicon oxide,by a heating means or by irradiation with ionizing radiation, it ispreferable that the composite material comprising the condensationpolymer produced through the hydrolysis of silicon oxide contain aninitiator.

The initiator may be a commercially available photopolymerizationinitiator.

Possible initiators are photoreaction initiators commercially availablefrom ciba-Geigy, Switzerland including IRUGACURE 185(1-hydroxycyclohexyl phenyl ketone), IRUGACURE 500 (1-hydroxycyclohexylphenyl ketone+benzophenone) and the like, GLOCURE 1173, 1116, 1396, 1274and 1020 commercially available from Merk, Switzerland, benzophenone,2-chlorothioxanethene, 2-methylthioxanthone, 2-isopropylthioxanthone,benzoin, 4,4-dimethoxybenzoin, benzoin ethyl ether, benzoin isopropylether, benzoin dimethyl ether, 1,1,1-trichloroacetophenone,diethoxyacetophenone and dibenzosuberon.

Particularly suitable thermal reaction initiators are diacyl peroxide,peroxydicarbonate, alkylperoxy ester, dialkyl peroxide, peroxy ketal,ketone peroxide and alkylperoxide organic peroxides.

Particularly preferable thermal reaction initiators are dibenzoilperoxide, perbenzoic tert-butyl and azobisisobutylonitrile.

Naturally, an ionic polymerization initiator may be used.

Particularly, a UV initiator that initiates cationic polymerizationreaction is effective with compound including R′ groups having epoxygroups, such as glycidyl oxypropyl trimethoxysilane, and expressed bygeneral formula (1).

In most cases, the result of curing by cations is more satisfactory thanthat of curing by a free radical initiator under the same conditions.

The composite material may contain an ordinary amount of initiator. Forexample, a composite substance containing 30 to 50% by weight of solidcontent may contain 0.5 to 2% by weight (to the total weight) ofinitiator.

According to the present invention, the coating film formed byapplication or printing is cured after drying.

The coating film may be cured by a know process depending on the type ofthe initiator contained therein, such as a heating process or anirradiation process using a UV lamp, a laser or the like.

It is known that a thermal curing process is particularly advantageousto curing a coating film including R′ groups having epoxy groups and anirradiation curing process, in most cases, is advantageous to curing acoating film containing R′ groups having unsaturated C—C bonds.

According to the present invention, a silicon compound or siliconcompounds expressed by R′SiR₃, where R′ denotes a group stable tohydrolysis and capable of being polymerized by heat and/or ionizingradiation, and R denotes an OH group and/or a group subject tohydrolysis.

It is desirable that R′ of the general formula R′SiR₃ is an epoxy atomicgroup or a group including an atomic group having a C—C double bond.

A glycidyl oxyalkyl group, particularly, a glycidyl oxyalkyl grouphaving an alkyl part having one to four carbon atomic groups is anexample of the group including an epoxy atomic group. Particularlypreferable group is a y-glycidyl oxypropyl group.

Preferably, the group R′ of the general formula R′SiR₃, having an atomicgroup having a C—C double bond is selectively substituted alkenyl andalkynyl groups, such as a straight chain, a side chain or a cyclic grouphaving 2 to 20, preferably, 2 to 10 carbon atoms and at least one C—Cdouble bond. Particularly preferable groups as the group R′ are loweralkenyl groups, such as vinyl, 1- and 2-propenyl, butenyl, isobutenyl,phenyl vinyl and propargyl, or groups including atomic groups includingan alkynyl group, a methacryl group or an acrylic group.

In the general formula R′SiR₃, R is, for example, hydrogen, a halogen,an alkoxy group, a hydroxyl group, or an alkynylcarbonyl group.

According to the present invention, particularly preferable groups are ,for example, a methoxy group, an ethoxy group, an n-propoxy group, ani-propoxy group, a sec-butoxy group, a tert-butoxy group, an isobutoxygroup, a β-methoxyethoxy group, an acetyloxy group, a propionyloxygroup, a monomethylamino group, a monoethylamino group, a dimethylaminogroup, a diethylamino group, an N-ethylanilino group, a methylcarbonylgroup, an ethylcarbonyl group, a methoxycarbonyl group, anethoxycarbonyl group and the like.

The group R of the general formula R′SiR₃ does not remain in the finalproduct, is decomposed by hydrolysis, and the product of hydrolysis mustbe removed immediately or later by an appropriate method. Therefore, agroup not having any substituent and capable of being hydrolyzed into alower alcohol of a low molecular weight, such as methanol, ethanolpropanol or butanol, is particularly preferable as the group R. Thesilicon compound expressed by the general formula R′SiR₃ may be used inan entirely or partly condensed form, i.e., in a compound produced bythe partial hydrolysis of the silicon compound, individually or incombination with another hydrolyzable compound, such as anorganometallic compound.

Preferably, such an oligomer is a partially condensed substance solublein a reaction medium, having the shape of a straight or cyclic chain, alow molecular weight and a condensation degree in the range of, forexample, about 2 to 100, more preferably, in the range of about 2 to 6,such as polyorganosiloxane.

Specific examples of substances capable of being effectively used as thesilicon compound expressed by the general formula R′SiR₃ areγ-(meta)acryloxypropyl trimethoxysilane, vinyl trichlorosilane, vinyltrimethoxysilane, vinyl triethoxysilane, vinyltris(β-methoxyethoxy)silane and γ-glycidyl oxypropyl trimethoxysilane.

Preferably, the silicon compound expressed by the general formula R′SiR₃is not used individually. Preferably, the silicon compound is mixed withone or some of organometallic compounds expressed by general formulaMR_(n), where M denotes an element, such as silicon, aluminum, titanium,zirconium, vanadium, boron and tin, R denotes an OH group and/or aeasily hydrolyzable group and n denotes the valence of the metallicelement, that is generally used for producing glass and ceramicmaterials, and the compounds are converted into hydrates ofcorresponding oxides by hydrolysis preferably, complete hydrolysis.

A metallic element contained in the organometallic compound expressed bythe general formula MR_(n) is, for example, silicon, aluminum titanium,zirconium, vanadium, boron or tin. It goes without saying that thepresent invention may use an organometallic compound containing ametallic element other than those mentioned above.

In the organometallic compound expressed by the general formula MR_(n),R may be either the same or different and may be defined similarly tothe R of the general formula R′SiR₃ expressing the silicon compound.

Preferably, the organometallic compound expressed by the general formulaMR_(n) and the silicon compound expressed by the general formula R′SiR₃are used in a mixture having the molar ratio of the organometalliccompound to the silicon compound in the range of 1:99 to 99:1.

The material forming the coating film of the present invention maycontain, in addition to the silicon compound expressed by the generalformula R′SiR₃ and the organometallic compound expressed by the generalformula MR_(n) one or some kinds of resins having hydrogen bond forminggroups as a binder or binders.

Possible resins having hydrogen bond forming groups are, for example,polymers having hydroxyl groups and their derivatives, such as polyvinylalcohol, polyvinyl acetal, ethylene-vinyl alcohol copolymers, phenolicresins, methylol melamine resins and their derivatives, polymers havingcarboxyl groups and their derivatives, such as polymers or copolymers ofpolymerizing unsaturated acids including poly(meta)acrylic acid, maleicanhydride and itaconic acid, and their esters, such as polymers orcopolymers of vinyl esters including vinyl acetate, (meta)acrylic acidesters including methyl methacrylate, polymers having ether bonds, suchas polyalkylene oxide, polyoxyalkylene glycol and polyvinyl ether,silicone resins, polymers having amide bonds, such as a >N(COR) bond (Ris hydrogen atom, an alkyl group which may have a substituent or an arylgroup which may have a substituent), polyvinyl pyrrolidone havinga >N(O) bond and its derivatives, polyurethane resins having urethanebonds, polymers having urea bonds and polymers having amide bonds.

According to the present invention, the resin having hydrogen bondforming groups may be used with a mixture of the silicon compoundexpressed by the general formula R′SiR₃ and the organometallic compoundexpressed by the general formula MR_(n) and the amount of the resinhaving hydrogen bond forming groups to be used is such that the weightratio of the resin having hydrogen bond forming groups to the mixture ofthe silicon compound and the organometallic compound is in the range of1:99 to 99:1, preferably, 5:30.

EXAMPLES

Examples of the third embodiment will be described hereinafter.

Example 1

(1) A roll of a 50 μm thick polyvinyl fluoride sheet (PVF sheet) wasmounted on a feed roll of a plasma chemical vapor deposition system. A50Å thick deposite dsilicon oxide thin film as a deposition-resistantprotective film was deposited on a treated surface of the polyvinylfluoride sheet treated for adhesion improvement under the followingdeposition condition.

Deposition Conditions:

Reaction gas mixing ratio: Hexamethyldicyloxane:Oxygen: Helium=5:5:5(unit: slm)

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 3.8×10⁻² mbar

Power supplied to cooling electrode drum: 15 kW

Sheet moving speed: 100 m/min

(2) A roll of the 50 μm thick polyvinyl fluoride sheet (PVF sheet)provided with the deposition-resistant protective film was mounted onthe feed roll of a plasma chemical vapor deposition system, and a 800 Åthick deposited silicon oxide thin film was deposited on thedeposition-resistant protective film of the polyvinyl fluoride sheetunder the following deposition conditions.

Deposition Conditions

Reaction gas mixing ratio: Hexamethyldicyloxane: Oxygen: Helium =5:10:10(Unit: slm)

Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

Vacuum in deposition chamber: 6.0×10⁻² mbar

Power supplied to cooling electrode drum: 20 kW

Sheet moving speed: 80 m/min

The 800 Å thick deposited silicon oxide film formed on the surface ofthe polyvinyl fluoride sheet was subjected to a corona discharge processto form a corona-processed surface and to increase the surface tensionof the deposited silicon oxide film from 35 dyne to 60 dyne. Coronadischarge power was 10 kW and the sheet was moved at a moving speed of100 m/min.

(3) Then, 25% by mole aluminum sec-butyrate was dropped at longintervals into a mixture of 45% by mole methacryl oxypropyltrimethoxysilane and 30% by mole methyl trimethoxysilane heated at roomtemperature while the mixture was stirred moderately. After all aluminumsec-butyrate had been dropped, the mixture was stirred for five minutesand was cooled to 15° C.

An amount of water equal to 1/15 of an amount was water necessary forcomplete hydrolysis was dropped into the mixture while the mixture wasstirred.

The mixture was stirred for additional five minutes, and then was cooledto 8° C.

Hydrolysis was completed and a coating composite material was prepared.

The coating composite material thus prepared was applied by a gravureroll coating process to the corona-processed surface of the depositedsilicon oxide film formed in (2) in a coating film, the coating film wasdried at 120° C. for 1 hr to form a coating film of 1.0 g/m² (dry state)in coating rate. Thus a protective sheet in accordance with the presentinvention for a solar battery module was fabricated.

(4) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the coating film of the protective sheet facing inside and thesurface of the 38 μm thick biaxially oriented polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet. Those component layers were laminated byusing adhesive layers of an acrylic resin to complete a solar batterymodule.

(5) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer was used instead ofthe 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 2

(1) A roll of a 50 μm thick polyvinyl fluoride film was mounted on afeed roll of a continuous vacuum evaporation system. The 50 μm thickpolyvinyl fluoride film was unwound and wound around a coating drum. A800 Å thick deposited aluminum oxide film was deposited on thedeposition-resistant protective film of the polyvinyl fluoride sheetunder the following conditions by a reactive evaporation process of anelectron beam (EB) heating system, in which aluminum was used as anevaporation source and oxygen gas was supplied to the continuous vacuumevaporation system.

Deposition Conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

EB power: 40 kW

Film moving speed: 600 m/min

Subsequently, the 800 Å thick deposited aluminum oxide film formed onthe surface of the polyvinyl fluoride sheet was processed by aglow-discharge plasma process to form a plasma-processed surface. Theglow-discharge plasma process was carried out by a glow-discharge plasmaproducing apparatus of 1500 W in plasma output immediately after thedeposition of the 800 Å thick deposited aluminum oxide film. In theglow-discharge plasma process, an oxygen/argon mixed gas of 19/1 inO₂/Ar ratio was supplied so that the pressure of the oxygen/argon mixedgas is maintained at 6×10⁻⁵ torr and the processing speed was 420 m/min.

(2) A mixture of 25 g of ethyl silicate, 25 g of ethanol, 86 g of 2Nhydrochloric acid and 1.51 g of water was heated at 80° C. and wasstirred for 1 to 2 hr.

The molar ratio of ethyl silicate to water of the mixture was 1:1:51.

Then, 2.5 g of epoxy silane (SH6040, Commercially available fromToray-Dou Corning) was added to the mixture and the mixture was stirred.

Then, 1.7 g of a 10% polyvinyl alcohol aqueous solution (polyvinylalcohol having a polymerization degree of 2000 available from Kuraray)was added to the mixture and the mixture was stirred for 1 to 2 hr. Whenthe mixture turned transparent, 0.1 g of 32% by weightN,N-dimethylbenzylamine ethanol solution was added to prepare acomposite coating material.

The coating composite material thus prepared was applied to theplasma-processed surface of the deposited aluminum oxide film formed in(1) by a gravure roll coating process in a film of 1.0 g/m² in coatingrate to complete a protective sheet for a solar battery module.

(3) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the coating film of the front surface protective sheet facinginside and the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet). Example3

(1) A roll of a 50 μm thick polyvinyl fluoride film (PVF film) wasmounted on a feed roll of a plasma chemical vapor deposition system. A500 Å thick deposited silicon oxide thin film was deposited on one ofthe surfaces of the polyvinyl fluoride film under the followingconditions.

Deposition Conditions:

Reaction gas mixing ratio: Hexamethyldisiloxane/oxygen/helium=1/10/10(Unit: slm)

Vacuum in vacuum chamber: 5.0×10⁻⁵ mbar

Vacuum in deposition chamber: 6.0×10⁻² mbar

Power supplied to cooling electrode drum: 20 kW

Film moving speed: 80 m/min

Surface for deposition: Corona-processed surface

The surface of the 500 Å thick deposited silicon oxide thin film formedon the polyvinyl fluoride film was subjected to a corona dischargeprocess to form a corona-processed surface and to increase the surfacetension of the deposited silicon oxide thin film from 35 dyne to 60dyne. Corona discharge power was 10 kW and the sheet was moved at amoving speed of 100 m/min.

(2) A roll of the polyvinyl fluoride film provided with thecorona-processed deposited silicon oxide thin film was mounted on a feedroll of a continuous vacuum evaporation system. The polyvinyl fluoridefilm was unwound and wound around a coating drum and a 500 Å thickdeposited aluminum oxide thin film was deposited on the corona-processedsurface of the deposited silicon oxide thin film formed on the polyvinylfluoride film by a reactive vacuum evaporation process of an electronbeam (EB) heating system. Aluminum was used as an evaporation source andoxygen gas was supplied to the continuous vacuum evaporation system.

Deposition Conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

EB power: 40 kW

Film moving speed: 600 m/min

A protective sheet in accordance with the present invention for a solarbattery module was completed by subjecting the 500 Å thick depositedaluminum oxide thin film formed on the surface of the polyvinyl fluoridesheet to a glow-discharge plasma process to form a plasma-processedsurface. The glow-discharge plasma process was carried out by aglow-discharge plasma producing apparatus of 1500 w in plasma outputimmediately after the deposition of the 500 Å thick deposited aluminumoxide thin film. In the glow-discharge plasma process, an oxygen/argonmixed gas of 19/1 in O₂/Ar ratio was supplied so that the pressure ofthe oxygen/argon mixed gas is maintained at 6×10⁻⁵ torr and theprocessing speed was 420 m/min.

(3) The plasma-processed surface of the deposited aluminum oxide filmformed in (2) was coated with a film of the composite coating materialprepared in Example 1. The film of the composite coating material wasdried at 120° C. for 1 hr to form a coating film of 1.0 g/m² (dry state)in coating rate to complete a protective sheet in accordance with thepresent invention for a solar battery module.

(4 ) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the coating film facing inside and the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

(5) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) containing anultraviolet absorber was used instead of the 50 μm thick polyvinylfluoride film (PVF film) containing an ultraviolet absorber.

Example 4

(1) A roll of a 50 μm thick polyvinyl fluoride sheet (PVF sheet) wasmounted on a feed roll of a continuous vacuum evaporation system. Thepolyvinyl fluoride sheet was unwound and wound around a coating drum.A50 Å thick deposited aluminum oxide thin film as a deposition-resistantprotective film was deposited on a treated surface of the polyvinylfluoride film treated for adhesion improvement by a reactive vacuumevaporation process of an electron beam (EB) heating system under thefollowing conditions.

Deposition Conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 2.1×⁻⁶ mbar

EB power: 20 kW

Film moving speed: 500 m/min

(2) A 800 Å thick deposited aluminum oxide film was formed by a methodsimilar to that of (2) of Example 2 on the deposition-resistantprotective film, i.e., the deposited aluminum oxide film, of the 50 μmthick polyvinyl fluoride sheet by a reactive vacuum evaporation processof an electron beam (EB) heating system. The surface of the depositedaluminum oxide film was subjected to a plasma process to form aplasma-processed surface.

(3) The plasma-processed surface of the deposited aluminum oxide filmformed in (2) was coated with a film of the composite coating materialprepared in Example 2 by a gravure roll coating process. The film of thecomposite coating material was dried at 120° C. for 1 hr to form acoating film of 2.0 g/m² (dry state) in coating rate to complete aprotective sheet in accordance with the present invention for a solarbattery module.

(4) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the coating film facing inside and the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

(5) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 5

(1) Protective sheets that are the same as the protective sheet inExample 1 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the coating films of the front surface and the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 50 μm thick fluorocarbon resin sheets ofan ethylene-tetrafluoroethylene copolymer (ETFE) were used instead ofthe 50 μm thick polyvinyl fluoride sheets (PVF sheet).

Example 6

(1) Protective sheets that are the same as the protective sheet inExample 2 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the coating films of the front surface and the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 50 μm thick fluorocarbon resin sheets ofan ethylene-tetrafluoroethylene copolymer (ETFE) were used instead ofthe 50 μm thick polyvinyl fluoride sheets (PVF sheet).

Example 7

(1) Protective sheets that are the same as the protective sheet inExample 3 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the coating films of the front surface and the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 50 μm thick fluorocarbon resin sheets ofan ethylene-tetrafluoroethylene copolymer (ETFE) containing anultraviolet absorber were used instead of the 50 μm thick polyvinylfluoride sheets (PVF sheets) containing the ultraviolet absorber.

Example 8

(1) Protective sheets that are the same as the protective sheet inExample 4 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the coating films of the front surface and the back surfaceprotective sheet facing inside and with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 50 μm thick fluorocarbon resin sheets ofan ethylene-tetrafluoroethylene copolymer (ETFE) were used instead ofthe 50 μm thick polyvinyl fluoride sheets (PVF sheets).

Example 9

(1) A protective sheet that is the same as the protective sheet inExample 1 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a3 mm thick glass sheet, a 400 μm thick ethylene-vinyl acetate copolymersheet, a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the coating film of the back surface protectivesheet facing inside and with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the 3 mm thick glass sheet, and laminating those componentlayers by using adhesive layers of an acrylic resin.

(2) A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 50 μm thick fluorocarbon resin sheetof an ethylene-tetrafluoroethylene copolymer (ETFE) was used instead ofthe 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 10

(1) A protective sheet that is the same as the protective sheet inExample 2 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with thecoating film of the back surface protective sheet facing inside and withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the 50 μm thickpolyvinyl fluoride sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

(2) A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 50 μm thick fluorocarbon resin sheetof an ethylene-tetrafluoroethylene copolymer (ETFE) was used instead ofthe 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 11

(1) A protective sheet that is the same as the protective sheet inExample 3 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with thecoating film of the back surface protective sheet facing inside and withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the 50 μm thickpolyvinyl fluoride sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

(2) A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 50 μm thick fluorocarbon resin sheetof an ethylene-tetrafluoroethylene copolymer (ETFE) was used instead ofthe 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Examples 12 to 15

Front surface protective sheets in accordance with the present inventionand solar battery modules of the same components as those of Example 1were fabricated by the same processes by using plastic sheets inExamples 12 to 15 instead of the 50 pm thick polyvinyl fluoride sheet(PVF sheet).

Example 12: 100 μm thick polydicyclopentadiene resin sheet

Example 13: 100 μm thick polycarbonate resin sheet

Example 14: 100 μm thick polyacrylic resin sheet

Example 15: 100 μm thick polyethylene terephthalate resin sheet

Examples 16 to 19

Front surface protective sheets in accordance with the present inventionand solar battery modules of the same components as those of Example 2were fabricated by the same processes by using plastic sheets inExamples 16 to 19 instead of the 50 μm thick polyvinyl fluoride sheet(PVF sheet).

Example 16: 100 μm thick polydicyclopentadiene resin sheet

Example 17: 100 μm thick polycarbonate resin sheet

Example 18: 100 μm thick polyacrylic resin sheet

Example 19: 100 μm thick polyethylene terephthalate resin sheet

Example 20

(1) A 500 Å thick deposited silicon oxide film was formed on a surfaceof a 50 μm thick polyvinyl fluoride sheet (PVF sheet) by aradio-frequency induction heating process, in which 99.9% pure siliconmonoxide (SiO) was evaporated in a vacuum of 1×10⁻⁴ torr.

Subsequently, the surface of the 500 Å thick deposited silicon oxidefilm formed on the polyvinyl fluoride sheet was subjected to a coronadischarge process to increase the surface tension of the same from 35dyne to 60 dyne. Corona discharge power was 10 kW and the sheet wasmoved at a moving speed of 100 m/min.

(2) The coating composite material prepared in Example d1 was applied tothe corona-processed surface of the deposited silicon oxide film by agravure roll coating process in a coating film, the coating film wasdried at 120° C. for 1 hr to form a coating film of 1.0 g/m² (dry state)in coating rate. Thus a protective sheet in accordance with the presentinvention for a solar battery module was fabricated.

(3) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the coating film facing inside and the surface of the 38 μm thickbiaxially oriented polyethylene terephthalate film provided with thesolar cells facing the front surface protective sheet. Those componentlayers were laminated by using adhesive layers of an acrylic resin tocomplete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-vinyl acetate copolymer containing an ultravioletabsorber was instead of the 50 μm thick polyvinyl fluoride sheet (PVFsheet) containing an ultraviolet absorber.

Example 21

(1) A roll of the 50 μm thick polyvinyl fluoride sheet (PVF sheet) wasmounted on the feed roll of a plasma chemical vapor deposition system,and a 800 Å thick deposited silicon oxide thin film was deposited on oneof the surfaces of the polyvinyl fluoride sheet under the followingdeposition conditions.

Deposition Conditions

Reaction gas mixing ratio: Hexamethyldicyloxane: Oxygen: Helium=1:10:10(Unit: slm)

Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

Vacuum in deposition chamber: 6.0×10⁻² mbar

Power supplied to cooling electrode drum: 20 kW

Sheet moving speed: 80 m/min

The 800 Å thick deposited silicon oxide film formed on the surface ofthe polyvinyl fluoride sheet was subjected to a corona discharge processto form a corona-processed surface and to increase the surface tensionof the deposited silicon oxide film from 35 dyne to 60 dyne. Coronadischarge power was 10 kW and the sheet was moved at a moving speed of100 m/min.

(2) The coating composite material prepared in Example 1 was applied bya gravure roll coating process to the corona-processed surface of thedeposited silicon oxide film in a film. The film was dried at 120° C.for 1 hr to form a coating film of 1.0 g/m² (dry state)in coating rate.Thus a protective sheet in accordance with the present invention for asolar battery module was fabricated.

(3) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the coating film of the front surface protective sheet facinginside and the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer was used instead ofthe 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 22

(1) A roll of a 50 μm thick polyvinyl fluoride film was mounted on afeed roll of a continuous vacuum evaporation system. The 50 μm thickpolyvinyl fluoride film was unwound and wound around a coating drum. A800 Å thick deposited aluminum oxide film was deposited on one of thesurfaces of the of the polyvinyl fluoride sheet under the followingconditions by a reactive evaporation process of an electron beam (EB)heating system, in which aluminum was used as an evaporation source andoxygen gas was supplied to the continuous vacuum evaporation system.

Deposition Conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

EB power: 40 kW

Film moving speed: 600 m/min

Subsequently, the 800 Å thick deposited aluminum oxide film formed onthe surface of the polyvinyl fluoride sheet was processed by aglow-discharge plasma process to form a plasma-processed surface. Theglow-discharge plasma process was carried out by a glow-discharge plasmaproducing apparatus of 1500 w in plasma output immediately after thedeposition of the 800 Å thick deposited aluminum oxide film. In theglow-discharge plasma process, an oxygen/argon mixed gas of 19/1 inO₂/Ar ratio was supplied so that the pressure of the oxygen/argon mixedgas is maintained at 6×10⁻⁵ torr and the processing speed was 420 m/min.

(2) The composite coating material prepared in Example 2 was applied tothe plasma-processed surface of the deposited aluminum oxide film by agravure roll coating process in a film. The film was dried at 120° C.for 1 hr to form a coating film of 1.0 g/m² in coating rate (dry state).Thus, a protective sheet in accordance with the present invention for asolar battery module was fabricated.

(3) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the coating film of the front surface protective sheet facinginside and the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

COMPARATIVE EXAMPLE 1

A solar battery module was fabricated by superposing a 3 mm thick glasssheet as a back surface protective sheet, a 400 μm thick ethylene-vinylacetate copolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film in that orderwith the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing the 50μm thick biaxially oriented polyethylene terephthalate film, andlaminating those component layers by using adhesive layers of an acrylicresin.

COMPARATIVE EXAMPLE 2

A solar battery module was fabricated by superposing a 50 μm thickpolyvinyl fluoride sheet (PVF sheet) as a front surface protectivesheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μmthick biaxially oriented polyethylene terephthalate film provided withan array of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and a 50 μm thick biaxially orientedpolyethylene terephthalate film in that order with the surface of the 38μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the 50 μm thick polyvinyl fluoridesheet, and laminating those component layers by using adhesive layers ofan acrylic resin.

COMPARATIVE EXAMPLE 3

A solar battery module was fabricated by superposing a 100 μm thickpolydicyclopentadiene sheet as a front surface protective sheet, a 400μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with an array ofamorphous silicon solar cells, a 400 μm thick ethylene-vinyl acetatecopolymer sheet and a 50 μm thick biaxially oriented polyethyleneterephthalate sheet in that order with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

COMPARATIVE EXAMPLE 4

A solar battery module was fabricated by using 50 μm thick polyvinylfluoride sheets (PVF sheets) as a front surface protective sheet and aback surface protective sheet. The solar battery module was fabricatedby superposing one of the 50 μm thick polyvinyl fluoride sheets (PVFsheets) as a front surface protective sheet, a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the other 50 μm thick polyvinyl fluoride sheet (PVF sheet) asa back surface protective sheet in that order with the surface of the 38μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet,and laminating those component layers by using adhesive layers of anacrylic resin.

COMPARATIVE EXAMPLE 5

A solar battery module was fabricated by using 100 μm thickpolydicyclopentadiene sheets as a front surface protective sheet and aback surface protective sheet. The solar battery module was fabricatedby superposing one of the 100 μm thick polydicyclopentadiene sheets as afront surface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and theother 100 μm thick polydicyclopentadiene sheet in that order with thesurface of the 38 μm thick polyethylene terephthalate film provided withthe array of amorphous silicon solar cells facing the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

EXPERIMENTS

The protective sheets in Examples 1 to 22 of the present invention andthose in Comparative examples 1 to 5 were subjected to totaltransmittance measurement. The solar battery modules in Examples 1 to 22and Comparative examples 1 to 5 were subjected to solar battery moduleevaluation tests.

(1) Total Transmittance Measurement

Total transmittance (%) of each of the protective sheets in Examples 1to 22 and Comparative examples 1 to 5 against the total transmittance ofthe base sheet as a reference total transmittance was measured by acolor computer.

(2) Solar Battery Module Evaluation Tests

The solar battery modules were subjected to environmental tests inconformity to conditions specified in JIS C8917-1989. Photovoltaicoutput of the solar battery modules was measured before and afterenvironmental tests.

(3) Moisture Permeability and Oxygen Permeability

The moisture permeabilities of the protective sheets in Examples 1 to 22and Comparative examples 1 to 5 were measured in an atmosphere of 40° C.and 90% RH by a moisture permeability measuring apparatus (PERMATRAN,MOCON, USA). The oxygen permeabilities of the protective sheets inExamples 1 to 22 and Comparative examples 1 to 5 were measured in anatmosphere of 23° C. and 90% RH by an oxygen permeability measuringapparatus (OXTRAN, MOCON, USA).

Measured data is tabulated in Table 3-1.

TABLE 3-1 Total Moisture oxygen Output trans- permea- permea- reductionmittance bility bility ratio (%) (g/m³/24 hr) (cc/m²/24 hr/atm) (%)Example 1 93 0.3 0.4 3 Example 2 92 0.4 0.5 2 Example 3 93 0.3 0.3 2Example 4 90 0.4 0.6 2 Example 5 92 0.4 0.4 1 Example 6 93 0.3 0.3 1Example 7 90 0.4 0.5 1 Example 8 91 0.3 0.4 1 Example 9 93 0.4 0.3 3Example 10 91 0.1 0.4 1 Example 11 91 0.1 0.3 1 Example 12 92 0.2 0.3 2Example 13 92 0.4 0.5 3 Example 14 90 0.3 0.2 2 Example 15 90 0.3 0.4 3Example 16 92 0.1 0.2 1 Example 17 91 0.4 0.4 3 Example 18 91 0.3 0.5 3Example 19 90 0.3 0.4 2 Example 20 93 0.4 0.5 3 Example 21 93 0.3 0.5 3Example 22 93 0.4 0.5 2 Comparative 89 25.0 80.0 18 Example 1Comparative 93 27.0 28.0 15 Example 2 Comparative 92 1.1 200.0 10Example 3 Comparative 93 27.0 28.0 12 Example 4 Comparative 93 1.0 200.09 Example 5

In table 3-1, moisture permeability is expressed in a unit ofg/m²/day·40° C.·100% RH, and oxygen permeability is expressed in a unitof cc/m²/day·23° C.·90% RH.

As obvious from Table 3-1, the protective sheets in Examples 1 to 22have high total transmittances, respectively, and are excellent inmoisture impermeability and oxygen impermeability.

Incidentally, the protective sheets in Examples 1 to 22 had oxygenpermeabilities in an atmosphere of 25° C. and 90% RH not greater than2.0 cm³/m²·day·atm and moisture permeabilities in an atmosphere of 40°C. and 100% RH mpy htrsyrt yjsm 3/0 g/m²·day·atm.

The output reduction ratios of the solar battery modules employing theprotective sheets in Examples 1 to 22 were low.

The protective sheets in Comparative examples 1 to 5 had high totaltransmittances, respectively. However, the moisture impermeabilities andthe oxygen impermeabilities of the protective sheets in Comparativeexamples 1 to 5 were low. Consequently, the output reduction ratios ofthe solar battery modules employing the protective sheets in Comparativeexamples 1 to 5 were high.

As apparent from the foregoing description, the present invention uses aplastic sheet as abase sheet, forms a transparent, vitreous depositedinorganic oxide thin film, such as a silicon oxide thin film or analuminum oxide thin film, on one of the surfaces of the plastic sheet,and fabricates a protective sheet for a solar battery module by forminga coating film of a composite material comprising a condensation polymerproduced through the hydrolysis of a silicon compound; the protectivesheet thus fabricated is used as the front surface protective sheet orthe back surface protective sheet of a solar battery module; the solarbattery module is fabricated by, for example, superposing the protectivesheet as a front surface protective sheet, a filler layer, a filmprovided with solar cells, i.e., photovoltaic cells, a filler layer andthe protective sheet as a back surface protective sheet in that order ina superposed structure with the deposited inorganic oxide thin filmsfacing inside, bringing the component layers of the superposed structureinto close contact by vacuum and bonding together those component layersby a lamination process using hot pressing; and the protective sheettransmits sunlight at a high transmittance, is excellent in strength,weather resistance, heat resistance, water resistance, light resistance,wind endurance, hailstorm resistance, chemical resistance, moistureresistance and soil resistance, has a high impermeability to moistureand oxygen, limits performance degradation due to aging to the leastextent, very durable, has excellent protective ability, and can be usedfor the stable fabrication of a low-cost, safe solar battery module.

The materials mentioned in the description of the first and the secondembodiment are applicable to the third embodiment.

FOURTH EMBODIMENT

The present invention will be described hereinafter with reference tothe accompanying drawings.

In this description, the term “sheet” is used in its broad sense todenote both sheets and films, and the term “film” is used in its broadsense to denote both sheets and films.

Protective sheets in accordance with the present invention for solarbattery modules and solar battery modules employing the protectivesheets will be described with reference to the accompanying drawings.FIGS. 16, 17, 18, 19 and 20 are typical sectional views of protectivesheets in examples in a fourth embodiment according to the presentinvention for a solar battery module, and FIGS. 21, 22 and 23 aretypical sectional views of solar battery modules employing theprotective sheet shown in FIG. 16.

Referring to FIG. 16, a protective sheet A in a first example of thefourth embodiment of the present invention for a solar battery module isa laminated structure constructed by laminating at least two basicstructures each comprising a fluorocarbon resin sheet (weather-resistantsheet) 1 and a deposited inorganic oxide film 2 formed on one of thesurfaces of the fluorocarbon resin sheet 1.

A surface-treated layer 3 may be formed in the fluorocarbon resin sheet1, and a coating film 103 of a polymer produced through the hydrolysisof a silicon compound may be formed on the deposited inorganic oxidefilm 2.

As shown in FIG. 17, a protective sheet A₁ in a second example of thefourth embodiment for a solar battery module is a laminated sheet formedby laminating at least two basic structures each comprising afluorocarbon resin sheet 1 and a deposited inorganic oxide thin film 2formed on one of the surfaces of the fluorocarbon resin sheet 1 by usingan adhesive layer 203.

As shown in FIG. 18 a protective sheet A₃ in a third example of thefourth embodiment for a solar battery module is a laminated sheet formedby laminating at least two basic structures each comprising afluorocarbon resin sheet 1 and a deposited inorganic oxide thin film 2formed on one of the surfaces of the fluorocarbon resin sheet 1, and aresin sheet 204 having a high strength by using adhesive layers 203 sothat the resin sheet 204 is sandwiched between the basic structures.

As shown in FIG. 19, a protective sheet A₃ in a fourth example of thefourth embodiment for a solar battery module is a laminated sheet formedby laminating at least two basic structures each comprising afluorocarbon resin sheet 1 and a multilayer film 4 comprising at leasttwo deposited inorganic oxide thin films 2 and formed on one of thesurfaces of the fluorocarbon resin sheet 1.

As shown in FIG. 20, a protective sheet A₄ in a fifth example of thefourth embodiment for a solar battery module is a laminated sheet formedby laminating at least two basic structures each comprising afluorocarbon resin sheet 1, and a composite film consisting of a firstdeposited inorganic oxide thin film 2 a formed by a chemical vapordeposition process on one of the surfaces of the fluorocarbon resinssheet 1 and a second deposited inorganic oxide thin film 2 b formed of amaterial different from that of the first deposited inorganic oxide thinfilm 2 a by a physical vapor deposition process on the first depositedinorganic oxide thin film 2 a.

Those protective sheets are only examples of the protective sheet in thefourth embodiment and the present invention is not limited thereto.

For example, when laminating at least the two basic structures eachconsisting of the fluorocarbon resin sheet and the deposited inorganicoxide thin film, the basic structures may be superposed with therespective deposited inorganic oxide thin films thereof facing eachother or with the fluorocarbon resin sheet of one of the basicstructures and the deposited inorganic oxide thin film of the otherbasic structure facing each other.

A solar battery module employing this protective sheet A embodying thepresent invention and shown in FIG. 16 will be described by way ofexample. Referring to FIG. 21, a solar battery module T employs theprotective sheet A shown in FIG. 16 as its front surface protectivesheet 11. The solar battery module T is fabricated by superposing thefront surface protective sheet 11(A), a filler layer 12, a photovoltaiclayer 13 of solar cells, a filler layer 14 and a generally known backsurface protective sheet 15 in that order in a superposed structure, andsubjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing. Either of the surfaces of the frontsurface protective sheet 11 may face inside.

Another solar battery module T₂ shown in FIG. 22 employs the protectivesheet A shown in FIG. 16 as its back surface protective sheet 16. Thesolar battery module T₂ is fabricated by superposing a generally knownfront surface protective sheet 17, a filler layer 12, a photovoltaiclayer 13 of solar cells, a filler layer 14 and the back surfaceprotective sheet 16(A) in that order in a superposed structure, andsubjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing.

A third solar battery module T₃ shown in FIG. 23 employs the protectivesheet A shown in FIG. 16 as its front surface protective sheet 11 andits back surface protective sheet 16. The solar battery module T₃ isfabricated by superposing the front surface protective sheet 11(A), afiller layer 12, a photovoltaic layer 13 of solar cells, a filler layer14 and the protective sheet 16(A) in that order in a superposedstructure, and subjecting the superposed structure to a generally knownforming process, such as a lamination process, in which those componentlayers of the superposed structure are brought into close contact byvacuum and are bonded together by hot pressing. Either of the surfacesof each of the protective sheets 11 and 16 may face inside.

The foregoing protective sheets in accordance with the present inventionand the foregoing solar battery modules employing those protectivesheets are examples intended to illustrate the invention and not to beconstrued to limit the scope of the invention.

For example, the foregoing solar battery modules may comprise additionallayers for sunlight absorption, reinforcement or the like.

Description will be given of methods of forming the protective sheet bylaminating at least the two basic structures each comprising thefluorocarbon resin sheet and the deposited inorganic oxide thin film,and forming the solar battery module employing the protective sheets.There are various possible methods.

A first method in accordance with the present invention uses at leastthe two basic structures each comprising the fluorocarbon resin sheet 1and the deposited inorganic oxide thin film 2, and laminates the twobasic structures by using the adhesive layer 203.

A second method in accordance with the present invention uses at leastthe two basic structures each comprising the fluorocarbon resin sheet 1and the deposited inorganic oxide thin film 2, and laminates the twobasic structures by using the adhesive layer 203 extruded individuallybetween the two basic structures or in a coextrusion mode.

A third method in accordance with the present invention uses at leastthe two basic structures each comprising the fluorocarbon resin sheet 1and the deposited inorganic oxide thin film 2, sandwiches thehigh-strength resin sheet 204 between the two basic structures, andlaminates the component layers by using adhesive layers.

The foregoing methods of laminating at least the two basic structureseach comprising the fluorocarbon resin sheet and the deposited inorganicoxide thin film are only examples and the present invention is notlimited thereto.

When necessary, the surface of the deposited inorganic oxide thin film 2formed on the fluorocarbon resin sheet 1 or the surface of thefluorocarbon resin sheet 1 to be bonded to another surface may beprocessed for adhesion improvement by a surface pretreatment process,such as a corona discharge process, an ozone process, a low-temperatureor atmospheric pressure plasma process, a glow-discharge process, anoxidation process using a chemical or the like.

The surface pretreatment process may be an independent process to becarried out after forming the deposited inorganic oxide thin film. Whenthe surface treatment process is a low-temperature plasma process or aglow discharge process, the surface pretreatment process may be carriedout in an in-line processing mode in a process for forming the depositedinorganic oxide thin film, which is effective in reducing themanufacturing cost.

The surface of the fluorocarbon resin sheet provided with the depositedinorganic oxide thin film is finished by the surface pretreatmentprocess for the adhesion improvement of the same. The improvement ofadhesion can be achieved also by forming a layer of a primer, anundercoater, an anchoring agent or the like.

Suitable materials for forming the coating layer are, for example,composite resins containing a polyester resin, a polyurethane resin, anacrylic resin or the like as a principal component of a vehicle.

The coating layer may be formed of a coating material of, for example, asolvent type, an aqueous solution type or an emulsion type by a rollcoating process, a gravure roll coating process, a kiss-roll coatingprocess or the like.

Suitable materials for forming the adhesive layer for bonding togetherthe superposed layers are polyvinyl acetate adhesives, polyacrylateadhesives including homopolymers of ethyl acrylate, butyl acrylate and2-ethylhexylester acrylate, and copolymers of those homopolymers andmethyl methacrylate, acrylonitrile or styrene, cyanoacrylate adhesives,ethylene copolymer adhesives including copolymers of ethylene andmonomers including vinyl acetate, ethyl acrylate, acrylic acid,methacrylic acid and the like, cellulose adhesives, polyester adhesives,polyamide adhesives, polyimide adhesives, amino resin adhesivesincluding urea resins and melamine resins, phenolic resin adhesives,epoxy adhesives, polyurethane adhesives, reactive (meta)acrylicadhesives, rubber adhesives including styrene-butadiene rubbers,chloroprene rubbers and nitrile rubbers, silicone adhesives, inorganicadhesive including alkaline metal silicate and low-melting glass and thelike.

Those adhesives may be of any one of an aqueous type, a solution type,an emulsion type and dispersion type, may be of any one of formsincluding a film, a sheet, powder or a solid, and may be of any one ofbonding types including a chemical reaction type, a solventvolatilization type, a hot melt type, a hot pressing type and the like.

The adhesive may be applied to the sheet by, for example, a roll coatingprocess, a gravure roll coating process, a kiss-roll coating process andthe like or may be printed on the sheet by a printing process.

The fusible, extrudable adhesive resin for forming an extruded adhesiveresin layer in the laminating process may be any one or a mixture ofsome of fusible resins including low-density polyethylenes,medium-density polyethylenes, high-density polyethylenes, linearlow-density polyethylenes, polypropylenes, ethylene-vinyl acetatecopolymers, ionomers, ethylene-ethyl acrylate copolymers,ethylene-acrylate copolymers, ethylene-methacrylic acid copolymers,ethylene-propylene copolymers, methyl pentene polymers, acid-modifiedpolyolefin resins produced by modifying polyolefin resins, such aspolyethylenes or polypropylenes, by an unsaturated carboxylic acid, suchas acrylic acid, methacrylic acid, maleic acid, maleic anhydride,fumaric acid, itaconic acid or the like, polyvinyl acetate resins,polyester resins, polystyrene resins, cyclic polyolefin resins,ethylene-a-olefin copolymers produced by polymerization using ametallocene catalyst, and the like.

The extruded adhesive resin layer is formed of one or some of theforegoing resins by an extrusion or a coextrusion process.

When laminating layers by using the extruded adhesive layer, ananchoring layer of a bonding assistant, such as an anchoring agent, maybe used to bond the layers firmly together.

Possible anchoring agents are, for example, organic titanium compounds,such as alkyltitanate, isocyanates, polyethylene imines, polybutadienesand the like. The anchoring agent may be either oil-soluble orwater-soluble.

Desirably, the anchoring agent is applied by a coating process, such asa roll coating process, a gravure roll coating process, a kiss-rollcoating process or the like, to the layer in a coating film of 0.1 to 5g/m² (dry state) in coating rate.

The third may use a laminating adhesive for laminating the layers.

The high-strength resin sheets to be laminated may be resin films orresin sheets excellent in physical and chemical strength, dimensionalstability, weather resistance, heat resistance, water resistance, lightresistance, chemical resistance, insulating property, flexibility,bending property, workability and the like. Possible films or sheets aretough films or sheets of polyester resins including ethylene-vinylacetate copolymers, polyethylene terephthalates, polybutyleneterephthalates, polyethylene naphthalates and polytetramethyleneterephthalates, polyolefin resins including polyethylenes,polypropylenes, and ethylene-propylene copolymers, polyamide resinsincluding nylon 12 and nylon 66, polyimide resins including polyimides,polyamidimides and polyetherimides, fluorocarbon resins includingpolytetrafluoroethylenes, polytrifluoroethylenes, polyvinilidenefluorides and polyvinyl fluorides, polyether sulphones, polyetherketones, polyphenylene sulfides, polyarylates, polyesterethers, aromaticpolyamides, polycarbonates, cyclic polyolefins and the like.

The resin films or sheets may be extruded or coextruded films or sheets,and may be nonoriented, uniaxially oriented or biaxially oriented.Desirably, the thickness of the resin films or sheets is in the range ofabout 6 to 300 μm, preferably, in the range of 10 to 100 μm.

When laminating sheets with a high-strength sheet sandwiched between thesheets, a laminating adhesive may be used in addition to one of theforegoing adhesives.

The laminating adhesive may be any one of laminating adhesives of asolvent type, an aqueous type or an emulsion type including single- ortwo-component, hardening or nonhardening vinyl resins, (meta)acrylicresins, polyamide resins, polyester resins, polyurethane resins, epoxyresins, phenolic resins and rubbers.

The laminating adhesive may contain an adhesion promoting agent, such asa silane coupling agent, and/or one or some of additives including anultraviolet absorber, an oxidation inhibitor, a stabilizer and the like.

Desirably, the laminating adhesive is applied by a coating process, suchas a roll coating process, a gravure roll coating process, a kiss-rollcoating process or the like, to the sheet in a coating film of 0.1 to 10g/m² (dry state) in coating rate.

Particularly desirable resin sheets among the foregoing high-strengthresin sheets are extruded or coextruded films or sheets of one or someof ethylene-vinyl acetate copolymers, polyethylene resins and cyclicpolyolefin resins. Possible cyclic polyolefin resin films or sheets arethose of, for example, cyclic diene polymers including cyclopentadieneand its derivatives, dicyclopentadiene and its derivatives,cyclohexadiene and its derivatives, norbornadiene and its derivatives,or one or some transparent cyclic polyolefin resin consisting of one orsome of copolymers of those cyclic dienes, and olefin monomers includingethylene, propylene, 4-methyl-1-pentene, styrene, butadiene andisoprene.

Transparent cyclic polyolefin resins including cyclic diene polymers,such as cyclopentadiene and its derivatives+and dicyclopentadiene andits derivatives are particularly preferable because those transparentcyclic polyolefin resins are excellent in weather resistance and waterresistance, is transparent and is preferable from the viewpoint ofsunlight transmission.

The front surface protective sheets in accordance with the presentinvention for solar battery modules using the cyclic polyolefin resinfilms or sheets utilize the excellent properties of the cyclicpolyolefin resin films or sheets including mechanical properties,optical properties, weather resistance, heat resistance, waterresistance, light resistance, moisture resistance, soil resistance,chemical resistance and the like. The front surface protective sheet isequal in optical properties and durability to a glass sheet generallyused as a protective sheet, has satisfactory mechanical properties, andis more flexible and lighter than a glass sheet, excellent inworkability and easy to handle.

It is desirable that the cyclic polyolefin resin of the presentinvention has a visible light transmittance of 90% or above, preferably,95% or above and a property to transmit all incident sunlight.

The cyclic polyolefin resin film or sheet in accordance with the presentinvention is excellent in adhesion to a deposited inorganic oxide thinfilm or a fluorocarbon resin sheet, a two-layer laminated sheet formedby laminating the cyclic polyolefin resin film or sheet, and thedeposited inorganic oxide thin film or the fluorocarbon resin sheet hasa very high bonding strength, and the layers of the two-layer laminatedsheet does not delaminate. A two-layer barrier film consisting of adeposited inorganic oxide thin film and a cyclic polyolefin resin filmor sheet has a high impermeability to oxygen gas and moisture,particularly to moisture. Thus, the present invention provides a verysatisfactory front surface protective sheet having excellent propertiesincluding transparency, heat resistance, hot water resistance andaptitude for lamination.

Various compounding ingredients and additives may be added to theadhesive layer, the extruded adhesive resin layer or the high-strengthresin sheet to improve the workability, heat resistance, weatherresistance, mechanical properties, dimensional stability, oxidationresistance, slipperiness, releasability, flame retardancy, antifungalproperty, electric properties and the like. The amount of each of thecompounding ingredients and the additives is in the range of a verysmall percent to several tens percent and may optionally be determinedaccording to the purpose.

Commonly known additives, such as a lubricant, a crosslinking agent, anoxidation inhibitor, an ultraviolet absorber, a light stabilizer, afiller, a reinforcing material, a stiffener, an antistatic agent, aflame retarder, a flame-resistant agent, a foaming agent, an antifungusagent, a pigment and the like may be used. A modifying resin may beused.

According to the present invention, it is particularly preferable to usean ultraviolet absorber and/or an oxidation inhibitor among thoseadditives.

The ultraviolet absorber absorbs detrimental ultraviolet rays containedin sunlight, converts the energy of ultraviolet rays into harmlessthermal energy in its molecules to prevent active species that startsthe photodeterioration of polymers from being excited. One or some ofultraviolet absorbers, such as those of a benzophenone group, abenzotriazole group, a salicylate group, an acrylonitrile group,metallic complex salts, a hindered amine group and an inorganicultraviolet absorber, such as ultrafine titanium oxide powder (particlesize: 0.01 to 0.06 μm) or ultrafine zinc oxide powder (particle size:0.01 to 0.04 μm), may be used.

The oxidation inhibitor prevents the light deterioration or thermaldeterioration of polymers. Suitable oxidation inhibitors are, forexample, those of a phenol group, an amine group, a sulfur group, aphosphoric acid group and the like.

The ultraviolet absorber or the oxidation inhibitor may be anultraviolet absorbing polymer or an oxidation inhibiting polymerproduced by chemically bonding an ultraviolet absorber of thebenzophenone group or an oxidation inhibitor of the phenol group to theprincipal chains or the side chains of a polymer.

The ultraviolet absorber and/or the oxidation inhibitor content isdependent on the shape and density of particles and a preferableultraviolet absorber and/or the oxidation inhibitor content is in therange of about 0.1 to about 10% by weight.

When necessary, a surface-treated layer may be formed in a surface forbonding by a surface pretreatment process for adhesion improvement. Thesurface-treated layer may be formed by, for example, a corona dischargetreatment, an ozone treatment, an atmospheric or low-temperature plasmatreatment using oxygen gas or nitrogen gas, a glow discharge treatment,an oxidation treatment using a chemical or the like.

The surface pretreatment for adhesion improvement may form a layer of aprimer, an undercoater, an anchoring agent or the like.

The coating layer may be formed of, for example, a composite resincontaining a polyester resin, a polyurethane resin, an acrylic resin orthe like as a principal component of its vehicle.

The coating layer may be formed of a coating material of, for example, asolvent type, an aqueous solution type or an emulsion type by a rollcoating process, a gravure roll coating process, a kiss-roll coatingprocess or the like.

The surface pretreatment for adhesion improvement may form, as thesurface-treated layer, a nonbarrier deposited inorganic oxide thin filmof a thickness in the range of 20 to 100 Å, preferably, in the range of30 to 60 Å by a process similar to that for forming the depositedinorganic oxide thin film. an emulsion type by a roll coating process, agravure roll coating process a kiss-roll coating process or the like.

The surface pretreatment for adhesion improvement may form, as thesurface-treated layer, a nonbarrier deposited inorganic oxide thin filmof a thickness in the range of 20 to 100 Å, preferably, in the range of30 to 60 Å by a process similar to that for forming the depositedinorganic oxide thin film.

EXAMPLES

Examples of the fourth embodiment will be described hereinafter.

Example 1

(1) A roll of a 50 μm thick polyvinyl fluoride sheet (PVF sheet), i.e.,base sheet, was mounted on a feed roll of a continuous vacuumevaporation system. The polyvinyl fluoride sheet was unwound and woundaround a coating drum and a 500 Å thick deposited aluminum oxide thinfilm was deposited on a treated surface of the polyvinyl fluoride sheettreated for adhesion improvement by a reactive vacuum evaporationprocess of an electron beam (EB) heating system to form a coatedpolyvinyl fluoride sheet. Aluminum was used as an evaporation source andoxygen gas was supplied to the continuous vacuum evaporation system.

Deposition Conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

EB power: 40 kW

Sheet moving speed: 600 m/min

(2) The 500 Å thick deposited aluminum oxide thin film of the coatedpolyvinyl fluoride sheet was subjected to a glow-discharge plasmaprocess to form a plasma-processed surface. The glow-discharge plasmaprocess was carried out by a glow-discharge plasma producing apparatusof 1500 W in plasma output immediately after the deposition of the 500 Åthick deposited aluminum oxide thin film. In the glow-discharge plasmaprocess, an oxygen/argon mixed gas of 19/1 in O₂/Ar ratio was suppliedso that the pressure of the oxygen/argon mixed gas is maintained at6×10⁻⁵ torr and the processing speed was 420 m/min.

(3) A laminating adhesive layer of a two-component polyurethanelaminating adhesive was formed in 1.0 g/m² (dry state) in coating rateby a gravure roll coating process on the plasma-processed surface of thedeposited aluminum oxide film of each of two coated polyvinyl fluoridesheets similar to that formed by (1) and (2), the two coated polyvinylfluoride sheets were disposed with the laminating adhesive layersthereof facing each other, a 20 μm thick polydicyclopentadiene film wassandwiched between the coated polyvinyl fluoride sheets, and thosecomponent layers were laminated by a dry lamination process to completea protective sheet in accordance with the present invention for a solarbattery module.

(4) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the surface of the 38 μm thick biaxially oriented polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet. Those component layerswere laminated by using adhesive layers of an acrylic resin to completea solar battery module.

(5) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that a 20 μm thick polycyclopentadiene film wasused instead of the 20 μm thick polydicyclopentadiene sheet.

A fourth protective sheet in accordance with the present invention and afourth solar battery module of the same components were fabricated bythe same processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polyvinyl fluoride sheets bonded to thepolyvinyl fluoride sheet of the other coated polyvinyl fluoride sheet.

Example 2

(1) A roll of a 50 μm thick polyvinyl fluoride film (PVF film), i.e.,base sheet, was mounted on a feed roll of a plasma chemical vapordeposition system. A 500 Å thick deposited silicon oxide thin film wasdeposited on a treated surface of the polyvinyl fluoride film treatedfor adhesion improvement under the following conditions to form a coatedpolyvinyl fluoride sheet.

Deposition Conditions:

Reaction gas mixing ratio: Hexamethyldisilox- ane/oxygen/helium=1/10/10(Unit: slm)

Vacuum in vacuum chamber: 5.9×10⁻⁶ mbar

Vacuum in deposition chamber: 6.0×10⁻² mbar

Power supplied to cooling electrode drum: 20 kw

Film moving speed: 80 m/min

Surface for vapor deposition: Corona-processed surface

(2) The 500 Å thick deposited silicon oxide thin film of the coatedpolyvinyl fluoride film was subjected to a corona discharge process toform a corona-processed surface and to increase the surface tension ofthe deposited silicon oxide thin film from 35 dyne to 60 dyne. Coronadischarge power was 10 kW and the sheet was moved at a moving speed of100 m/min.

(3) A laminating adhesive layer of 1.0 g/m² (dry state) in coating ratewas formed on the corona-processed surface of the deposited siliconoxide film of each of two coated polyvinyl fluoride sheets similar tothat formed by (1) and (2), the two coated polyvinyl fluoride sheetswere disposed with the laminating adhesive layers thereof facing eachother, a 20 μm thick polydicyclopentadiene film was sandwiched betweenthe coated polyvinyl fluoride sheets, and those component layers werelaminated by a dry lamination process to complete a protective sheet inaccordance with the present invention for a solar battery module.

(4) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the surface of the 38 μm thick biaxially oriented polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet. Those component layerswere laminated by using adhesive layers of an acrylic resin to completea solar battery module.

(5) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that a 20 μm thick polycyclopentadiene film wasused instead of the 20 μm thick polydicyclopentadiene sheet.

A fourth protective sheet in accordance with the present invention and afourth solar battery module of the same components were fabricated bythe same processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited silicon oxidethin film of one of the coated polyvinyl fluoride sheets bonded to thepolyvinyl fluoride sheet of the other coated polyvinyl fluoride sheet.

Example 3

(1) A 50 μm thick polyvinyl fluoride film (PVF film) containing anultraviolet absorber was used as a base sheet. A 500 Å thick depositedsilicon oxide thin film was deposited on a surface of the polyvinylfluoride film under the same conditions as those in Example 2. Thesurface of the deposited silicon oxide thin film was subjected to acorona discharge process to form a corona-processed surface.

(2) A 500 Å thick deposited aluminum oxide thin film was deposited onthe corona-processed surface of the deposited silicon oxide thin filmformed on the polyvinyl fluoride film under the same conditions as thosein Example 1. A coated polyvinyl fluoride film was completed bysubjecting the surface of the deposited aluminum oxide thin film to aplasma process to form a plasma-processed surface therein.

(3) A laminating adhesive layer of a two-component ,polyurethaneadhesive containing a small amount of an ultraviolet absorber containingultrafine titanium oxide powder (particle size: 0.01 to 0.06 μm) wasformed in a coating rate of 5.0 g/m² (dry state) on the plasma-processedsurface of the deposited aluminum oxide film of each of two coatedpolyvinyl fluoride films similar to that formed by (1) and (2). The twocoated polyvinyl fluoride films were bonded together with the laminatingadhesive layers thereof in contact with each other to complete aprotective sheet in accordance with the present invention for a solarbattery module.

(4) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing thefront surface protective sheet. Those component layers were laminated byusing adhesive layers of an acrylic resin to complete a solar batterymodule.

(5) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resin filmof an ethylene-tetrafluoroethylene copolymer (ETFE) was used instead ofthe 50 μm thick polyvinyl fluoride film (PVF film).

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polyvinyl fluoride films weresuperposed and bonded together with the deposited aluminum oxide thinfilm of one of the coated polyvinyl fluoride films bonded to thepolyvinyl fluoride film of the other coated polyvinyl fluoride film.

Example 4

An anchoring layer of a polyurethane anchoring agent was formed in acoating rate of 0.5 g/m² (dry state) by a gravure roll coating processon the plasma-processed surface of the deposited aluminum oxide film ofeach of two coated polyvinyl fluoride sheets similar to that inExample 1. A 100 μm thick polydicyclopentadiene film was formed on theanchoring layer of each of the two coated polyvinyl fluoride sheets byan extrusion coating process. Thus a protective sheet in accordance withthe present invention for a solar battery module was completed.

A solar battery module employing the protective sheet as its frontsurface protective sheet was fabricated by the same processes as thosein Example 1.

Another protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a polycyclopentadiene film was usedinstead of the polydicyclopentadiene film.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polyvinyl fluoride sheets bonded to thepolyvinyl fluoride sheet of the other coated polyvinyl fluoride sheet.

Example 5

An anchoring layer of a polyurethane anchoring agent was formed in acoating rate of 0.5 g/m² (dry state) by a gravure roll coating processon the corona-processed surface of the deposited silicon oxide film ofeach of two coated polyvinyl fluoride sheets similar to that in Example2. A 30 μm thick polydicyclopentadiene film was formed on the anchoringlayer of each of the two coated polyvinyl fluoride sheets by anextrusion coating process. Thus a protective sheet in accordance withthe present invention for a solar battery module was fabricated.

A solar battery module employing the protective sheet as its frontsurface protective sheet was fabricated by the same processes as thosein Example 2.

Another protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a polynorbornadiene resin was usedinstead of the polydicyclopentadiene resin.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited silicon oxidethin film of one of the coated polyvinyl fluoride sheets bonded to thepolyvinyl fluoride sheet of the other coated polyvinyl fluoride sheet.

Example 6

A laminating adhesive layer of a two-component polyurethane laminatingadhesive containing an ultraviolet absorber containing ultrafinetitanium oxide powder (particle size: 0.01 to 0.06 μm) was formed in acoating rate of 1.0 g/m² (dry state) by a gravure roll coating processon the plasma-processed surface of the deposited aluminum oxide film ofeach of two coated polyvinyl fluoride sheets (PVF sheets) similar tothat in Example 1. A 20 μm thick polydicyclopentadiene film wassandwiched between the coated polyvinyl fluoride sheets, and thosecomponent layers were laminated by a dry lamination process to completea protective sheet in accordance with the present invention for a solarbattery module.

A solar battery module employing the protective sheet as its frontsurface protective sheet was fabricated by the same processes as thosein Example 1.

Another protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a polycyclopentadiene film was usedinstead of the polydicyclopentadiene film.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polyvinyl fluoride sheets bonded to thepolyvinyl fluoride sheet of the other coated polyvinyl fluoride sheet.

Example 7

(1) Protective sheets that are the same as the protective sheet inExample 1 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 50 μm thick fluorocarbon resin sheets ofan ethylene-tetrafluoroethylene copolymer (ETFE) were used instead ofthe 50 μm thick polyvinyl fluoride sheets (PVF sheet).

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that a 20 μm thick polycyclopentadiene film wasused instead of the 20 μm thick polydicyclopentadiene film.

A fourth protective sheet in accordance with the present invention and afourth solar battery module of the same components were fabricated bythe same processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polyvinyl fluoride sheets bonded to thepolyvinyl fluoride sheet of the other coated polyvinyl fluoride sheet.

Example 8

(1) Protective sheets that are the same as the protective sheet inExample 3 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 50 μm thick fluorocarbon resin sheets ofan ethylene-tetrafluoroethylene copolymer (ETFE) were used as the basesheet instead of the 50 μm thick polyvinyl fluoride sheets (PVF sheet).

Third protective sheets in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that a 20 μm thick polycyclopentadiene film wasused instead of the 20 μm thick polydicyclopentadiene film.

A fourth protective sheet in accordance with the present invention and afourth solar battery module of the same components were fabricated bythe same processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited silicon oxidethin film of one of the coated polyvinyl fluoride sheets bonded to thepolyvinyl fluoride sheet of the other coated polyvinyl fluoride sheet.

Example 9

(1) Protective sheets that are the same as the protective sheet inExample 3 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 50 μm thick fluorocarbon resin sheetof an ethylene-tetrafluoroethylene copolymer (ETFE) containing anultraviolet absorber was used instead of the 50 μm thick polyvinylfluoride sheet (PVF sheet) containing an ultraviolet absorber.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polyvinyl fluoride sheets bonded to thepolyvinyl fluoride sheet of the other coated polyvinyl fluoride sheet.

Example 10

(1) Protective sheets that are the same as the protective sheet inExample 4 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

A protective sheet in accordance with the present invention and anothersolar battery module of the same components were fabricated by the sameprocesses, except that a polycyclopentadiene resin was used instead ofthe polydicyclopentadiene resin.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polyvinyl fluoride sheets bonded to thepolyvinyl fluoride sheet of the other coated polyvinyl fluoride sheet.

Example 11

Protective sheets that are the same as the protective sheet in Example 5were used as the front surface protective sheet and the back surfaceprotective sheet of a solar battery module. The solar battery module wasfabricated by superposing the front surface protective sheet, a 400 μmthick ethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with an array ofamorphous silicon solar cells, a 400 μm thick ethylene-vinyl acetatecopolymer sheet and the back surface protective sheet in that order withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

Protective sheets in accordance with the present invention and anothersolar battery module of the same components were fabricated by the sameprocesses, except that a polynorbornadiene resin was used instead of thepolydicyclopentadiene resin.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited silicon oxidethin film of one of the coated polyvinyl fluoride sheets bonded to thepolyvinyl fluoride sheet of the other coated polyvinyl fluoride sheet.

Example 12

Protective sheets that are the same as the protective sheet in Example 6were used as the front surface protective sheet and the back surfaceprotective sheet of a solar battery module. The solar battery module wasfabricated by superposing the front surface protective sheet, a 400 μmthick ethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with an array ofamorphous silicon solar cells, a 400 μm thick ethylene-vinyl acetatecopolymer sheet and the back surface protective sheet in that order withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

Protective sheets in accordance with the present invention and anothersolar battery module of the same components were fabricated by the sameprocesses, except that a polycyclopentadiene film was used instead ofthe polydicyclopentadiene film.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polyvinyl fluoride sheets bonded to thepolyvinyl fluoride sheet of the other coated polyvinyl fluoride sheet.

Example 13

(1) A protective sheet that is the same as the protective sheet inExample 1 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a3 mm thick glass sheet, a 400 μm thick ethylene-vinyl acetate copolymersheet, a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the 3 mm thick glass sheet, and laminating those componentlayers by using adhesive layers of an acrylic resin.

(2) A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 50 μm thick fluorocarbon resin sheetof an ethylene-tetrafluoroethylene copolymer (ETFE) was used instead ofthe 50 μm thick polyvinyl fluoride sheet (PVF sheet).

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that a 20 μm thick polycyclopentadiene film wasused instead of the 20 μm thick polydicyclopentadiene film.

A fourth protective sheet in accordance with the present invention and afourth solar battery module of the same components were fabricated bythe same processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polyvinyl fluoride sheets bonded to thepolyvinyl fluoride sheet of the other coated polyvinyl fluoride sheet.

Example 14

(1) A protective sheet that is the same as the protective sheet inExample 2 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick polyvinyl fluoride sheet (PVF sheet), a 400 μm thickethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells, a 400 μm thick ethylene-vinyl acetate copolymersheet and the back surface protective sheet in that order with thesurface of the 38 μm thick polyethylene terephthalate film provided withthe array of amorphous silicon solar cells facing the 50 μm thickpolyvinyl fluoride sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

(2) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was used as abase sheet instead of the 50 μm thick polyvinyl fluoride sheet (PVFsheet).

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that a 20 μm thick polycyclopentadiene film wasused instead of the 20 μm thick polydicyclopentadiene film.

A fourth protective sheet in accordance with the present invention and afourth solar battery module of the same components were fabricated bythe same processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited silicon oxidethin film of one of the coated polyvinyl fluoride sheets bonded to thepolyvinyl fluoride sheet of the other coated polyvinyl fluoride sheet.

Example 15

(1) A protective sheet that is the same as the protective sheet inExample 3 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a100 μm thick polydicyclopentadiene sheet, a 400 μm thick ethylene-vinylacetate copolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and theback surface protective sheet in that order with the surface of the 38μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the 100 μm thickpolydicyclopentadiene sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer containing anultraviolet absorber(ETFE sheet) was used as a base sheet instead of the50 μm thick polyvinyl fluoride sheet (PVF sheet) containing anultraviolet absorber.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polyvinyl fluoride sheetseach provided with the deposited silicon oxide thin film and thedeposited aluminum oxide thin film were superposed and bonded togetherwith the deposited aluminum oxide thin film of one of the coatedpolyvinyl fluoride sheets bonded to the polyvinyl fluoride sheet of theother coated polyvinyl fluoride sheet.

COMPARATIVE EXAMPLE 1

A solar battery module was fabricated by superposing a 100 μm thickpolydicyclopentadiene sheet, i.e., base sheet, as a front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film in that order with the surfaceof the 38 μm thick polyethylene terephthalate film provided with thearray of amorphous silicon solar cells facing the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

COMPARATIVE EXAMPLE 2

A solar battery module was fabricated by superposing a 50 μm thickpolyvinyl fluoride sheet (PVF sheet), i.e., base sheet, as a frontsurface protective sheet, a 400 μm thick ethylene-vinyl acetatecopolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and a 50 μmthick biaxially oriented polyethylene terephthalate film in that orderwith the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

COMPARATIVE EXAMPLE 3

A solar battery module was fabricated by superposing a 100 μm thickpolydicyclopentadiene sheet, i.e., base sheet, as a front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 100 μm thickpolydicyclopentadiene sheet, i.e., base sheet, as a back surfaceprotective sheet in that order with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

COMPARATIVE EXAMPLE 4

A solar battery module was fabricated by superposing a 50 μm thickpolyvinyl fluoride film (PVF film), i.e., base sheet, as a front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick polyvinylfluoride film (PVF film), i.e., base sheet, as a back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

EXPERIMENTS

The protective sheets in Examples 1 to 15 of the present invention andthose in Comparative examples 1 to 4 were subjected to totaltransmittance measurement. The solar battery modules in Examples 1 to 15and Comparative examples 1 to 4 were subjected to solar battery moduleevaluation tests.

(1) Total Transmittance Measurement

Total transmittance (%) of each of the protective sheets in Examples 1to 15 and Comparative examples 1 to 4 against the total transmittance ofthe base sheet as a reference total transmittance was measured by acolor computer.

(2) Solar Battery Module Evaluation Tests

The solar battery modules were subjected to environmental tests inconformity to conditions specified in JIS C8917-1989. Photovoltaicoutput of the solar battery modules was measured before and afterenvironmental tests.

(3) Moisture Permeability and Oxygen Permeability

The moisture permeabilities of the protective sheets in Examples 1 to 15and Comparative examples 1 to 4 were measured in an atmosphere of 40° C.and 90% RH by a moisture permeability measuring apparatus (PERMATRAN,MOCON, USA). The oxygen permeabilities of the protective sheets inExamples 1 to 15 and Comparative examples 1 to 5 were measured in anatmosphere of 23° C. and 90% RH by an oxygen permeability measuringapparatus (OXTRAN, MOCON, USA).

Measured data is tabulated in Table 4-1.

TABLE 4-1 Total Moisture oxygen Output trans- permea- permea- reductionmittance bility bility ratio (%) (g/m²/24 hr) (cc/m²/24 hr/atm) (%)Example 1 91 0.2 0.4 2 Example 2 90 0.3 0.4 3 Example 3 92 0.1 0.2 1Example 4 93 0.3 0.6 3 Example 5 92 0.4 0.5 1 Example 6 90 0.2 0.4 3Example 7 91 0.2 0.3 2 Example 8 91 0.3 0.4 2 Example 9 92 0.1 0.1 1Example 10 92 0.3 0.5 2 Example 11 91 0.2 0.3 2 Example 12 90 0.1 0.1 1Example 13 93 0.3 0.2 2 Example 14 92 0.4 0.2 3 Example 15 91 0.2 0.3 3Comparative 93 1.2 200.0 10 Example 1 Comparative 93 26.7 27.5 15Example 2 Comparative 93 1.2 200.0 8 Example 3 Comparative 93 26.0 28.011 Example 4

In table 4-1, moisture permeability is expressed in a unit ofg/m²/day·40° C.·100% RH, and oxygen permeability is expressed in a unitof cc/m²/day·23° C.·90% RH.

As obvious from Table 4-1, the protective sheets in Examples 1 to 15have high total transmittances, respectively, and are excellent inmoisture impermeability and oxygen impermeability.

The output reduction ratios of the solar battery modules employing theprotective sheets in Examples 1 to 15 were low.

The protective sheets in Comparative examples 1 to 4 had high totaltransmittances, respectively. However, the moisture impermeabilities andthe oxygen impermeabilities of the protective sheets in Comparativeexamples 1 to 4 were low. Consequently, the output reduction ratios ofthe solar battery modules employing the protective sheets in Comparativeexamples 1 to 4 were high.

As apparent from the foregoing description, the present invention uses afluorocarbon resin sheet as a base sheet, fabricates a coatedfluorocarbon resin sheet by forming a transparent, vitreous depositedinorganic oxide thin film, such as a silicon oxide thin film or analuminum oxide thin film, on one of the surfaces of the fluorocarbonresin sheet, and fabricates a protective sheet for a solar batterymodule by laminating at least two coated fluorocarbon resin sheetssimilar to the foregoing coated fluorocarbon resin sheet by an adhesivelayer or the like, uses the protective sheet as the front surfaceprotective sheet or the back surface protective sheet of a solar batterymodule; fabricates a solar battery module by, for example, superposingthe protective sheet as a front surface protective sheet, a fillerlayer, a film provided with solar cells, i.e., photovoltaic cells, afiller layer and an ordinary back surface protective sheet in that orderin a superposed structure, bringing the component layers of thesuperposed structure into close contact by vacuum and bonding togetherthose component layers by a lamination process using hot pressing; andthe protective sheet transmits sunlight at a high transmittance, isexcellent in strength, weather resistance, heat resistance, waterresistance, light resistance, wind endurance, hailstorm resistance,chemical resistance, moisture resistance and soil resistance, has a highimpermeability to moisture and oxygen, limits performance degradationdue to aging to the least extent, very durable, has excellent protectiveability, and can be used for the stable fabrication of a low-cost, safesolar battery module.

The materials mentioned in the description of the first, the second andthe third embodiment are applicable to the fourth embodiment.

FIFTH EMBODIMENT

The present invention will be described hereinafter with reference toFIGS. 16 to 23 previously used in the description of the fourthembodiment.

In this description, the term “sheet” is used in its broad sense todenote both sheets and films, and the term “film” it used in its broadsense to denote both sheets and films.

Referring to FIG. 16, a protective sheet A in a first example of thefifth embodiment of the present invention for a solar battery module isa laminated structure constructed by laminating at least two basicstructures each comprising a cyclic polyolefin sheet(weather-resistantsheet) 1 and a deposited inorganic oxide film 2 formed on one of thesurfaces of the cyclic polyolefin sheet 1.

A surface-treated layer 3 may be formed in the cyclic polyolefin sheet1, and a coating film 103 of a polymer produced through the hydrolysisof a silicon compound may be formed on the deposited inorganic oxidefilm 2.

As shown in FIG. 17, a protective sheet A₁ in a second example of thefifth embodiment for a solar battery module is a laminated sheet formedby laminating at least two basic structures each comprising a cyclicpolyolefin sheet 1 and a deposited inorganic oxide thin film 2 formed onone of the surfaces of the cyclic polyolefin sheet 1 by using anadhesive layer 203.

As shown in FIG. 18 a protective sheet A₃ in a third example of thefourth embodiment for a solar battery module is a laminated sheet formedby laminating at least two basic structures each comprising a cyclicpolyolefin sheet 1 and a deposited inorganic oxide thin film 2 formed onone of the surfaces of the fluorocarbon resin sheet 1, and a resin sheet204 having a high strength by using adhesive layers 203 so that theresin sheet 204 is sandwiched between the basic structures.

As shown in FIG. 19, a protective sheet A₃ in a fourth example of thefifth embodiment for a solar battery module is a laminated sheet formedby laminating at least two basic structures each comprising a cyclicpolyolefin 1 and a multilayer film 4 comprising at least two depositedinorganic oxide thin films 2 and formed on one of the surfaces of thefluorocarbon resin sheet 1.

As shown in FIG. 20, a protective sheet A₄ in a fifth example of thefourth embodiment for a solar battery module is a laminated sheet formedby laminating at least two basic structures each comprising a cyclicpolyolefin sheet 1, and a composite film 5 consisting of a firstdeposited inorganic oxide thin film 2 a formed by a chemical vapordeposition process on one of the surfaces of the cyclic polyolefin sheet1 and a second deposited inorganic oxide thin film 2 b formed of amaterial different from that of the first deposited inorganic oxide thinfilm 2 a by a physical vapor deposition process on the first depositedinorganic oxide thin film 2 a.

Those protective sheets are only examples of the protective sheet in thefourth embodiment and the present invention is not limited thereto.

For example, when laminating at least the two basic structures eachconsisting of the cyclic polyolefin sheet and the deposited inorganicoxide thin film, the basic structures may be superposed with therespective deposited inorganic oxide thin films thereof facing eachother or with the cyclic polyolefin sheet of one of the basic structuresand the deposited inorganic oxide thin film of the other basic structurefacing each other.

A solar battery module employing this protective sheet A embodying thepresent invention and shown in FIG. 16 will be described by way ofexample. Referring to FIG. 21, a solar battery module T employs theprotective sheet A shown in FIG. 16 as its front surface protectivesheet 11. The solar battery module T is fabricated by superposing thefront surface protective sheet 11(A), a filler layer 12, a photovoltaiclayer 13 of solar cells, a filler layer 14 and a generally known backsurface protective sheet 15 in that order in a superposed structure, andsubjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing. Either of the surfaces of the frontsurface protective sheet 11 may face inside.

Another solar battery module T₂ shown in FIG. 22 employs the protectivesheet A shown in FIG. 16 as its back surface protective sheet 16. Thesolar battery module T₂ is fabricated by superposing a generally knownfront surface protective sheet 17, a filler layer 12, a photovoltaiclayer 13 of solar cells, a filler layer 14 and the back surfaceprotective sheet 16(A) in that order in a superposed structure, andsubjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing.

A third solar battery module T₃ shown in FIG. 23 employs the protectivesheet A shown in FIG. 16 as its front surface protective sheet 11 andits back surface protective sheet 16.

The solar battery module T₃ is fabricated by superposing the frontsurface protective sheet 11(A), a filler layer 12, a photovoltaic layer13 of solar cells, a filler layer 14 and the protective sheet 16(A) inthat order in a superposed structure, and subjecting the superposedstructure to a generally known forming process, such as a laminationprocess, in which those component layers of the superposed structure arebrought into close contact by vacuum and are bonded together by hotpressing. Either of the surfaces of each of the protective sheets 11 and16 may face inside.

The foregoing protective sheets in accordance with the present inventionand the foregoing solar battery modules employing those protectivesheets are examples intended to illustrate the invention and not to beconstrued to limit the scope of the invention.

For example, solar battery modules of different forms can be fabricatedby using the protective sheets shown in FIGS. 17 to 20, and theforegoing solar battery modules may comprise additional layers forsunlight absorption, reinforcement or the like.

Description will be given of methods of forming the protective sheet bylaminating at least the two basic structures each comprising the cyclicpolyolefin sheet and the deposited inorganic oxide thin film, andforming the solar battery module employing the protective sheets. Thereare various possible methods.

A first method in accordance with the present invention uses at leastthe two basic structures each comprising the cyclic polyolefin sheet 1and the deposited inorganic oxide thin film 2, and laminates the twobasic structures by using the adhesive layer 203.

A second method in accordance with the present invention uses at leastthe two basic structures each comprising the cyclic polyolefin sheet 1and the deposited inorganic oxide thin film 2, and laminates the twobasic structures by using the adhesive layer 203 extruded individuallybetween the two basic structures or in a coextrusion mode.

A third method in accordance with the present invention uses at leastthe two basic structures each comprising the cyclic polyolefin sheet 1and the deposited inorganic oxide thin film 2, sandwiches thehigh-strength resin sheet 204 between the two basic structures, andlaminates the component layers by using adhesive layers 203.

The foregoing methods of laminating at least the two basic structureseach comprising the cyclic polyolefin sheet and the deposited inorganicoxide thin film are only examples and the present invention is notlimited thereto.

When necessary, the surface of the deposited inorganic oxide thin film 2formed on the cyclic polyolefin sheet 1 or the surface of the cyclicpolyolefin sheet 1 to be bonded to another surface may be processed foradhesion improvement by a surface pretreatment process, such as acoronadischarge process, an ozone process, a low-temperature or atmosphericpressure plasma process, a glow-discharge process, an oxidation processusing a chemical or the like.

The surface pretreatment process may be an independent process to becarried out after forming the deposited inorganic oxide thin film. Whenthe surface treatment process is a low-temperature plasma process or aglow discharge process, the surface pretreatment process may be carriedout in an in-line processing mode in a process for forming the depositedinorganic oxide thin film, which is effective in reducing themanufacturing cost.

The surface of the cyclic polyolefin sheet provided with the depositedinorganic oxide thin film is finished by the surface pretreatmentprocess for the adhesion improvement of the same.

The improvement of adhesion can be achieved also by forming a layer of aprimer, an undercoater, an anchoring agent or the like, for example, onthe surface of the deposited inorganic oxide thin film or the surface ofthe cyclic polyolefin sheet.

Suitable materials for forming the coating layer are, for example,composite resins containing a polyester resin, a polyurethane resin, anacrylic resin or the like as a principal component of a vehicle.

The coating layer may be formed of a coating material of, for example, asolvent type, an aqueous solution type or an emulsion type by a rollcoating process, a gravure roll coating process, a kiss-roll coatingprocess or the like.

Methods of fabricating solar battery modules from those materials willbe described. A known method uses the protective sheet in accordancewith the present invention for a solar battery module as the frontsurface protective sheet or the back surface protective sheet of thesolar battery module. The method fabricates a solar battery module bysuperposing the protective sheet as a front surface protective sheet, afiller layer, a photovoltaic layer of solar cells, a filler layer, andan ordinary protective sheet or the protective sheet in accordance withthe present invention as a back surface protective sheet in that orderin a superposed structure, when necessary, interposes layers of othermaterials between the component layers of the superposed structure,bringing the component layers of the superposed structure into closecontact by vacuum and bonding together those component layers by alamination process using hot pressing.

When necessary, and adhesive, such as a fusible adhesive, a solventadhesive or a photocurable adhesive, containing, as a principalcomponent of its vehicle, a (meta)acrylic resin, an olefin resin, avinyl resin or the like may be used to enhance adhesion between thelayers.

When necessary, the surface to which the filler layer is to be bonded,such as the surface of the deposited inorganic oxide thin film of thefront or the back surface protective sheet of the solar battery moduleor the surface of the cyclic polyolefin sheet, may be treated by apretreatment process, such as a corona discharge process, ozone process,a low-temperature or atmospheric plasma process, a glow-dischargeprocess, an oxidation process using a chemical or the like, beforelaminating the filler layer or the like to one of the surfaces of thefront or the back surface protective sheet of the solar battery moduleto enhance adhesion between the contiguous layers.

The surface pretreatment for adhesion improvement can be achieved alsoby forming a coating layer of coating material, such as a primer, anundercoater, an anchoring agent or the like, on the surface of thedeposited inorganic oxide thin film or the surface of the fluorocarbonresin sheet.

The coating material may be a composite resin containing a polyesterresin, a polyurethane resin, an acrylic resin or the like as a principalcomponent of a vehicle.

The coating layer may be formed of a solvent coating material, anaqueous coating material or an emulsion coating material by a coatingprocess, such as a roll coating process, a gravure roll coating processor a kiss-roll coating process.

The surface pretreatment for adhesion improvement can be achieved byforming a nonbarrier deposited inorganic oxide thin film of a thicknessin the range of about 20 to 100 Å, preferably, in the range of 30 to 60Å as a surface-pretreated layer by the foregoing method of forming thedeposited inorganic oxide film on the surface contiguous with the fillerlayer, i.e., the surface of the cyclic polyolefin sheet or the depositedinorganic oxide thin film.

EXAMPLES

Examples of the fifth embodiment will be described hereinafter.

Example 1

(1) A roll of a 100 μm thick polydicyclopentadiene sheet, i.e., basesheet, was mounted on a feed roll of a continuous vacuum evaporationsystem. The polydicyclopentadiene sheet was unwound and wound around acoating drum and a 500 Å thick deposited aluminum oxide thin film wasdeposited on a treated surface of the polydicyclopentadiene sheettreated for adhesion improvement by a reactive vacuum evaporationprocess of an electron beam (EB) heating system to form a coatedpolydicyclopentadiene sheet. Aluminum was used as an evaporation sourceand oxygen gas was supplied to the continuous vacuum evaporation system.

Deposition Conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

EB power: 40 kW

Sheet moving speed: 600 m/min

(2) The 500 Å thick deposited aluminum oxide thin film of the coatedpolydicyclopentadiene sheet was subjected to a glow-discharge plasmaprocess to form a plasma-processed surface. The glow-discharge plasmaprocess was carried out by a glow-discharge plasma producing apparatusof 1500 W in plasma output immediately after the deposition of the 500 Åthick deposited aluminum oxide thin film. In the glow-discharge plasmaprocess, an oxygen/argon mixed gas of 19/1 in O₂/Ar ratio was suppliedso that the pressure of the oxygen/argon mixed gas is maintained at6×10⁻⁵ torr and the processing speed was 420 m/min.

(3) A laminating adhesive layer of a polyurethane laminating adhesiveconsisting of a polyesterpolyol resin containing 5% by weight ofbenzotriazole ultraviolet absorber, and a diisocyanate compound wasformed in 1.0 g/m² (dry state) in coating rate by a gravure roll coatingprocess on the plasma-processed surface of the deposited aluminum oxidefilm of one of two coated polydicyclopentadiene sheets similar to thatformed by (1) and (2). The two coated polydicyclopentadiene sheets weredisposed with the laminating adhesive layer of one of the coatedpolydicyclopentadiene sheet and the plasma-processed surface of thedeposited aluminum oxide thin film of the other coatedpolydicyclopentadiene sheet, and the two coated polydicyclopentadienesheets were laminated by a dry lamination process to form a protectivesheet for a solar battery module.

(4) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the surface of the 38 μm thick biaxially oriented polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet. Those component layerswere laminated by using adhesive layers of an acrylic resin to completea solar battery module.

(5) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadienesheet was used instead of the 100 μm thick polydicyclopentadiene sheet.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polydicyclopentadiene sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 2

(1) A roll of a 100 μm thick polydicyclopentadiene sheet, i.e., basesheet, was mounted on a feed roll of a plasma chemical vapor depositionsystem. A 500 Å thick deposited silicon oxide thin film was deposited ona treated surface of the polydicyclopentadiene sheet treated foradhesion improvement under the following conditions to form a coatedpolydicyclopentadiene sheet.

Deposition Conditions:

Reaction gas mixing ratio: Hexamethyldisiloxane/oxygen/helium=1/10/10(Unit: slm)

Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

Vacuum in deposition chamber: 6.0×10⁻² mbar

Power supplied to cooling electrode drum: 20 kW

Film moving speed: 80 m/min

Surface for vapor deposition: Corona-processed surface

(2) The 500 Å thick deposited silicon oxide thin film of the coatedpolydicyclopentadiene sheet was subjected to a corona discharge processto form a corona-processed surface and to increase the surface tensionof the deposited silicon oxide thin film from 35 dyne to 60 dyne. Coronadischarge power was 10 kW and the sheet was moved at a moving speed of100 m/min.

(3) A laminating adhesive layer of 1.0 g/m² (dry state) in coating rateof a polyurethane laminating adhesive consisting of a polyesterpolyolresin containing 1.5% by weight of a benzotriazole ultraviolet absorberand 1.t % by weight of a hindered amine photostabilizer, and adiisocyanate compound was formed on the corona-processed surface of thedeposited silicon oxide film of one of two coated polydicyclopentadienesheets similar to that formed by (1) and (2), the two coatedpolydicyclopentadiene sheets were disposed with the laminating adhesivelayer of one of the two coated polydicyclopentadiene sheets facing thecorona-processed surface of the other coated polydicyclopentadienesheet, and the two coated polydicyclopentadiene sheets were laminated bya dry lamination process to form a protective sheet in accordance withthe present invention for a solar battery module.

(4) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the surface of the 38 μm thick biaxially oriented polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet. Those component layerswere laminated by using adhesive layers of an acrylic resin to completea solar battery module.

(5) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadienewas used instead of the 100 μm thick polydicyclopentadiene sheet.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited silicon oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 3

(1) A 100 μm thick polydicyclopentadiene sheet containing an ultravioletabsorber was used as a base sheet. A 500 Å thick deposited silicon oxidethin film was deposited on a surface of the polydicyclopentadiene sheetunder the same conditions as those in Example 2. The surface of thedeposited silicon oxide thin film was subjected to a corona dischargeprocess to form a corona-processed surface.

(2) A 500 Å thick deposited aluminum oxide thin film was deposited onthe corona-processed surface of the deposited silicon oxide thin filmformed on the polydicyclopentadiene sheet under the same conditions asthose in Example 1. A coated polyvinyl fluoride film was completed bysubjecting the surface of the deposited aluminum oxide thin film to aplasma process to form a plasma-processed surface therein.

(3) A laminating adhesive layer of a polyurethane laminating adhesiveconsisting of a polyesterpolyol resin containing a small amount of anultraviolet absorber containing ultrafine titanium oxide powder(particlesize: 0.01 to 0.06 μm), and a diisocyanate compound was formedin a coating rate of 5.0 g/m² (dry state) on the plasma-processedsurface of the deposited aluminum oxide film of each of two coatedpolydicyclopentadiene sheets similar to that formed by (1) and (2) by agravure roll coating process. The two coated polydicyclopentadienesheets were bonded together with the laminating adhesive layers thereofin contact with each other to complete a protective sheet in accordancewith the present invention for a solar battery module.

(4) A solar battery module was fabricated by using the protective sheetthus fabricated as a front surface protective sheet. The front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film were superposed in that orderwith the surface of the 38 μm thick polyethylene terephthalate filmprovided with the array of amorphous silicon solar cells facing thefront surface protective sheet. Those component layers were laminated byusing adhesive layers of an acrylic resin to complete a solar batterymodule.

(5) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadienesheet was used instead of the 100 μm thick polydicyclopentadiene sheet.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polydicyclopentadiene sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 4

An anchoring layer of a polyurethane anchoring agent was formed in acoating rate of 0.5 g/m² (dry state) by a gravure roll coating processon the plasma-processed surface of the deposited aluminum oxide film ofeach of two coated polydicyclopentadiene sheets similar to that inExample 1. A 30 μm thick polydicyclopentadiene film was formed on theanchoring layer of each of the two coated polydicyclopentadiene sheetsby an extrusion coating process. Thus a protective sheet in accordancewith the present invention for a solar battery module was completed.

A solar battery module employing the protective sheet as its frontsurface protective sheet was fabricated by the same processes as thosein Example 1.

Another protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a polycyclopentadiene film was usedinstead of the polydicyclopentadiene film.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polydicyclopentadiene sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 5

An anchoring layer of a polyurethane anchoring agent was formed in acoating rate of 0.5 g/m² (dry state) by a gravure roll coating processon the corona-processed surface of the deposited silicon oxide film ofeach of two coated polydicyclopentadiene sheets similar to that inExample 2. A 30 μm thick polydicyclopentadiene film was formed on theanchoring layer of each of the two coated polydicyclopentadiene sheetsby an extrusion coating process. Thus a protective sheet in accordancewith the present invention for a solar battery module was fabricated.

A solar battery module employing the protective sheet as its frontsurface protective sheet was fabricated by the same processes as thosein Example 2.

Another protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a polynorbornadiene resin was usedinstead of the polydicyclopentadiene resin.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polydicyclopentadiene sheetswere superposed and bonded together with the deposited silicon oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 6

A laminating adhesive layer of a two-component polyurethane laminatingadhesive containing a small amount of an ultraviolet absorber containingultrafine titanium oxide powder (particle size: 0.01 to 0.06 μm) wasformed in a coating rate of 1.0 g/m² (dry state) by a gravure rollcoating process on the plasma-processed surface of the depositedaluminum oxide film of each of two coated polydicyclopentadiene sheetssimilar to that in Example 1. A 20 μm thick polydicyclopentadiene filmwas sandwiched between the laminating adhesive layers of the coatedpolydicyclopentadiene sheets, and those component layers were laminatedby a dry lamination process to complete a protective sheet in accordancewith the present invention for a solar battery module.

A solar battery module employing the protective sheet was fabricated bythe same processes as those in Example 1.

Another protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a polycyclopentadiene film was usedinstead of the polydicyclopentadiene film.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polydicyclopentadiene sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 7

(1) Protective sheets that are the same as the protective sheet inExample 1 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 100 μm thick polycyclopentadiene sheetswere used instead of the 100 μm thick polydicyclopentadiene sheets.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polydicyclopentadiene sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 8

(1) Protective sheets that are the same as the protective sheet inExample 2 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that 100 μm thick polycyclopentadiene sheetswere used as the base sheets instead of the 100 μm thickpolydicyclopentadiene sheets.

Third protective sheets in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polydicyclopentadiene sheetswere superposed and bonded together with the deposited silicon oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 9

(1) Protective sheets that are the same as the protective sheet inExample 3 were used as the front surface protective sheet and the backsurface protective sheet of a solar battery module. The solar batterymodule was fabricated by superposing the front surface protective sheet,a 400 μm thick ethylene-vinyl acetate copolymer sheet, a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells, a 400 μm thick ethylene-vinylacetate copolymer sheet and the back surface protective sheet in thatorder with the surface of the 38 μm thick polyethylene terephthalatefilm provided with the array of amorphous silicon solar cells facing thefront surface protective sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Protective sheets in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 100 μm thick polycyclopentadienesheet) containing an ultraviolet absorber was used instead of the 100 μmthick polydicyclopentadiene sheet containing an ultraviolet absorber.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polyvinyl fluoride sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 10

Protective sheets that are the same as the protective sheet in Example 4were used as the front surface protective sheet and the back surfaceprotective sheet of a solar battery module. The solar battery module wasfabricated by superposing the front surface protective sheet, a 400 μmthick ethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with an array ofamorphous silicon solar cells, a 400 μm thick ethylene-vinyl acetatecopolymer sheet and the back surface protective sheet in that order withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

A protective sheet in accordance with the present invention and anothersolar battery module of the same components were fabricated by the sameprocesses, except that a polycyclopentadiene resin was used instead ofthe polydicyclopentadiene resin.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polydicyclopentadiene sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 11

Protective sheets that are the same as the protective sheet in Example 5were used as the front surface protective sheet and the back surfaceprotective sheet of a solar battery module. The solar battery module wasfabricated by superposing the front surface protective sheet, a 400 μmthick ethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with an array ofamorphous silicon solar cells, a 400 μm thick ethylene-vinyl acetatecopolymer sheet and the back surface protective sheet in that order withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

Protective sheets in accordance with the present invention and anothersolar battery module of the same components were fabricated by the sameprocesses, except that a polycyclopentadiene resin was used instead ofthe polydicyclopentadiene resin.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polydicyclopentadiene sheetswere superposed and bonded together with the deposited silicon oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 12

Protective sheets that are the same as the protective sheet in Example 6were used as the front surface protective sheet and the back surfaceprotective sheet of a solar battery module. The solar battery module wasfabricated by superposing the front surface protective sheet, a 400 μmthick ethylene-vinyl acetate copolymer sheet, a 38 μm thick biaxiallyoriented polyethylene terephthalate film provided with an array ofamorphous silicon solar cells, a 400 μm thick ethylene-vinyl acetatecopolymer sheet and the back surface protective sheet in that order withthe surface of the 38 μm thick polyethylene terephthalate film providedwith the array of amorphous silicon solar cells facing the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

Protective sheets in accordance with the present invention and anothersolar battery module of the same components were fabricated by the sameprocesses, except that a polycyclopentadiene film was used instead ofthe polydicyclopentadiene film.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polydicyclopentadiene sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 13

(1) A protective sheet that is the same as the protective sheet inExample 1 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a3 mm thick glass sheet, a 400 μm thick ethylene-vinyl acetate copolymersheet, a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and the back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the 3 mm thick glass sheet, and laminating those componentlayers by using adhesive layers of an acrylic resin.

(2) A protective sheet in accordance with the present invention andanother solar battery module of the same components were fabricated bythe same processes, except that a 100 μm thick polycyclopentadiene wasused instead of the 100 μm thick polydicyclopentadiene sheet.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polydicyclopentadiene sheetswere superposed and bonded together with the deposited aluminum oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 14

(1) A protective sheet that is the same as the protective sheet inExample 2 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a50 μm thick fluorocarbon resin sheet, a 400 μm thick ethylene-vinylacetate copolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and theback surface protective sheet in that order with the surface of the 38μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the 50 μm thick fluorocarbon resinsheet, and laminating those component layers by using adhesive layers ofan acrylic resin.

(2) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadienesheet was used as a base sheet instead of the 100 μm thickpolydicyclopentadiene sheet.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polydicyclopentadiene sheetswere superposed and bonded together with the deposited silicon oxidethin film of one of the coated polydicyclopentadiene sheets bonded tothe polydicyclopentadiene sheet of the other coatedpolydicyclopentadiene sheet.

Example 15

(1) A protective sheet that is the same as the protective sheet inExample 3 was used as the back surface protective sheet of a solarbattery module. The solar battery module was fabricated by superposing a100 μm thick polydicyclopentadiene sheet, a 400 μm thick ethylene-vinylacetate copolymer sheet, a 38 μm thick biaxially oriented polyethyleneterephthalate film provided with an array of amorphous silicon solarcells, a 400 μm thick ethylene-vinyl acetate copolymer sheet and theback surface protective sheet in that order with the surface of the 38μm thick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the 100 μm thickpolydicyclopentadiene sheet, and laminating those component layers byusing adhesive layers of an acrylic resin.

(2) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 100 μm thick polycyclopentadienesheet containing an ultraviolet absorbero was used as a base sheetinstead of the 100 μm thick polydicyclopentadiene sheet containing anultraviolet absorber.

A third protective sheet in accordance with the present invention and athird solar battery module of the same components were fabricated by thesame processes, except that the two coated polydicyclopentadiene sheetseach provided with the deposited silicon oxide thin film and thedeposited aluminum oxide thin film were superposed and bonded togetherwith the deposited aluminum oxide thin film of one of the coatedpolydicyclopentadiene sheets bonded to the polydicyclopentadiene sheetof the other coated polydicyclopentadiene sheet.

COMPARATIVE EXAMPLE 1

A solar battery module was fabricated by superposing a 100 μm thickpolydicyclopentadiene sheet, i.e., base sheet, as a front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film in that order with the surfaceof the 38 μm thick polyethylene terephthalate film provided with thearray of amorphous silicon solar cells facing the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

COMPARATIVE EXAMPLE 2

A solar battery module was fabricated by superposing a 50 μm thickpolyvinyl fluoride sheet (PVF sheet), i.e., base sheet, as a frontsurface protective sheet, a400 μm thick ethylene-vinyl acetate copolymersheet, a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick biaxiallyoriented polyethylene terephthalate film in that order with the surfaceof the 38 μm thick polyethylene terephthalate film provided with thearray of amorphous silicon solar cells facing the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

COMPARATIVE EXAMPLE 3

A solar battery module was fabricated by superposing a 100 μm thickpolydicyclopentadiene sheet, i.e., base sheet, as a front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 100 μm thickpolydicyclopentadiene sheet, i.e., base sheet, as a back surfaceprotective sheet in that order with the surface of the 38 μm thickpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet, andlaminating those component layers by using adhesive layers of an acrylicresin.

COMPARATIVE EXAMPLE 4

A solar battery module was fabricated by superposing a 50 μm thickpolyvinyl fluoride film (PVF film), i.e., base sheet, as a front surfaceprotective sheet, a 400 μm thick ethylene-vinyl acetate copolymer sheet,a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells, a 400 μm thickethylene-vinyl acetate copolymer sheet and a 50 μm thick polyvinylfluoride film (PVF film), i.e., base sheet, as a back surface protectivesheet in that order with the surface of the 38 μm thick polyethyleneterephthalate film provided with the array of amorphous silicon solarcells facing the front surface protective sheet, and laminating thosecomponent layers by using adhesive layers of an acrylic resin.

EXPERIMENTS

The protective sheets in Examples 1 to 15 of the present invention andthose in comparative examples 1 to 4 were subjected to totaltransmittance measurement. The solar battery modules in Examples 1 to 15and Comparative examples 1 to 4 were subjected to solar battery moduleevaluation tests.

(1) Total Transmittance Measurement

Total transmittance (%) of each of the protective sheets in Examples 1to 15 and Comparative examples 1 to 4 against the total transmittance ofthe base sheet as a reference total transmittance was measured by acolor computer.

(2) Solar Battery Module Evaluation Tests

The solar battery modules were subjected to environmental tests inconformity to conditions specified in JIS C8917-1989. Photovoltaicoutput of the solar battery modules was measured before and afterenvironmental tests.

(3) Moisture Permeability and Oxygen Permeability

The moisture permeabilities of the protective sheets in Examples 1 to 15and Comparative examples 1 to 4 were measured in an atmosphere of 40° C.and 90% RH by a moisture permeability measuring apparatus (PERMATRAN,MOCON, USA). The oxygen permeabilities of the protective sheets inExamples 1 to 22 and Comparative examples 1 to 5 were measured in anatmosphere of 23° C. and 90% RH by an oxygen permeability measuringapparatus (OXTRAN, MOCON, USA).

Measured data is tabulated in Table 5-1.

TABLE 5-1 Total Moisture oxygen Output trans- permea- permea- reductionmittance bility bility ratio (%) (g/m²/24 hr) (cc/m²/24 hr/atm) (%)Example 1 92 0.2 0.4 2 Example 2 91 0.3 0.4 3 Example 3 90 0.1 0.2 1Example 4 93 0.3 0.6 3 Example 5 91 0.4 0.5 1 Example 6 92 0.2 0.4 3Example 7 92 0.2 0.4 1 Example 8 91 0.3 0.4 2 Example 9 90 0.1 0.2 1Example 10 93 0.3 0.6 2 Example 11 92 0.4 0.5 1 Example 12 92 0.2 0.4 1Example 13 92 0.2 0.4 5 Example 14 91 0.3 0.4 4 Example 15 90 0.1 0.2 3Comparative 92 1.2 200.0 10 Example 1 Comparative 93 26.3 27.2 15Example 2 Comparative 92 1.2 200.0 8 Example 3 Comparative 93 26.3 27.211 Example 4

In table 5-1, moisture permeability is expressed in a unit ofg/m²/day·40° C.·100% RH, and oxygen permeability is expressed in a unitof cc/m²/day·23° C.·90% RH.

As obvious from Table 5-1, the protective sheets in Examples 1 to 15have high total transmittances, respectively, and are excellent inmoisture impermeability and oxygen impermeability.

The output reduction ratios of the solar battery modules employing theprotective sheets in Examples 1 to 15 were low.

The protective sheets in Comparative examples 1 to 4 had high totaltransmittances, respectively. However, the moisture impermeabilities andthe oxygen impermeabilities of the protective sheets in Comparativeexamples 1 to 4 were low. Consequently, the output reduction ratios ofthe solar battery modules employing the protective sheets in Comparativeexamples 1 to 4 were high.

As apparent from the foregoing description, the present invention uses acyclic polyolefin sheet as a base sheet, fabricates a coatedfluorocarbon resin sheet by forming a transparent, vitreous depositedinorganic oxide thin film, such as a silicon oxide thin film or analuminum oxide thin film, on one of the surfaces of the cyclicpolyolefin sheet, and fabricates a protective sheet for a solar batterymodule by laminating at least two coated cyclic polyolefin sheetssimilar to the foregoing coated cyclic polyolefin sheet by an adhesivelayer or the like, uses the protective sheet as the front surfaceprotective sheet or the back surface protective sheet of a solar batterymodule; fabricates a solar battery module by, for example, superposingthe protective sheet as a front surface protective sheet, a fillerlayer, a film provided with solar cells, i.e., photovoltaic cells, afiller layer and the protective sheet as a back surface protective sheetin that order in a superposed structure, bringing the component layersof the superposed structure into close contact by vacuum and bondingtogether those component layers by a lamination process using hotpressing; and the protective sheet transmits sunlight at a hightransmittance, is excellent in strength, weather resistance, heatresistance, water resistance, light resistance, wind endurance,hailstorm resistance, chemical resistance, moisture resistance and soilresistance, has a high impermeability to moisture and oxygen, limitsperformance degradation due to aging to the least extent, very durable,has excellent protective ability, and can be used for the stablefabrication of a low-cost, safe solar battery module.

The materials mentioned in the description of the first to the fourthembodiment are applicable to the fifth embodiment. by a laminationprocess using hot pressing; and the protective sheet transmits sunlightat a high transmittance, is excellent in strength, weather resistance,heat resistance, water resistance, light resistance, wind endurance,hailstorm resistance, chemical resistance, moisture resistance and soilresistance, has a high impermeability to moisture and oxygen, limitsperformance degradation due to aging to the least extent, very durable,has excellent protective ability, and can be used for the stablefabrication of a low-cost, safe solar battery module.

The materials mentioned in the description of the first to the fourthembodiment are applicable to the fifth embodiment.

SIXTH EMBODIMENT

The present invention will be described hereinafter with reference tothe accompanying drawings.

FIGS. 24 to 28 are typical sectional views of protective sheets inaccordance with the present invention for solar battery modules, andFIG. 29 is a typical sectional view of a solar battery module employinga protective sheet shown in FIG. 24.

Referring to FIG. 24, a front surface protective sheet A in a firstexample of the sixth embodiment of the present invention for a solarbattery module comprises a fluorocarbon resin sheet (weather-resistantsheet) 1 and deposited inorganic oxide film 2 deposited on one of thesurfaces of the fluorocarbon resin sheet 1. A soil resistant layer 303and/or an ultraviolet absorbing layer 304 is formed on one of thesurfaces of the fluorocarbon resin sheet 1.

Referring to FIG. 25, a front surface protective sheet A₁ in a secondexample of the sixth embodiment of the present invention for a solarbattery module comprises a fluorocarbon resin sheet 1, a depositedinorganic oxide thin film 2 deposited on one of the surface of thefluorocarbon resin sheet 1, an ultraviolet absorbing layer 304 formed onthe other surface of the fluorocarbon resin sheet 1, and asoil-resistant layer 303 formed on the ultraviolet absorbing layer 304.The soil-resistant layer 303 forms the outermost surface of the frontsurface protective sheet A₁.

Referring to FIG. 26, a front surface protective sheet A₂ in a thirdexample of the sixth embodiment of the present invention for a solarbattery module comprises a fluorocarbon resin sheet 1, a depositedinorganic oxide thin film 2 formed on one of the surfaces of thefluorocarbon resin sheet 1, a soil-resistant layer 303 formed on thesurface of the fluorocarbon resin sheet 1, and an ultraviolet absorbinglayer 304 formed on the deposited inorganic oxide thin film 2. Thesoil-resistant layer 303 forms the outermost surface of the frontsurface protective sheet A₂.

In the front surface protective sheets shown in FIGS. 25 and 26, thesurface of the fluorocarbon resin sheet 1 may be processed to form asurface-treated layer 3 therein.

Referring to FIG. 27, a front surface protective sheet A₃ in a fourthexample of the sixth embodiment of the present invention for a solarbattery module comprises a fluorocarbon resin sheet 1, a multilayer film4 consisting of at least two deposited inorganic oxide thin films 2 andformed on one of the surfaces of the fluorocarbon resin sheet 1, and asoil-resistant layer 303 and/or an ultraviolet asorbing layer 304 formedon one of or both the surfaces of the fluorocarbon resin sheet 1provided with the multilayer film 4.

Referring to FIG. 28, a front surface protective sheet A₄ in a fifthexample of the sixth embodiment of the present invention for a solarbattery module comprises a fluorocarbon resin sheet 1, a multilayer film5 consisting of at lest a deposited inorganic oxide thin film 2 a formedby a chemical vapor deposition process and a deposited inorganic oxidefilm 2 b formed on the deposited inorganic oxide thin film 2 a by aphysical vapor deposition process, and formed on one of the surfaces ofthe fluorocarbon resin film 1, a soil-resistant layer 303 and/or anultraviolet absorber layer 304 formed on one of or both the surfaces ofthe fluorocarbon resin sheet 1.

Referring to FIG. 29, a solar battery module T employs the protectivesheet A shown in FIG. 24 as its front surface protective sheet. Thesolar battery module T is fabricated by superposing the front surfaceprotective sheet A, a filler layer 12, a photovoltaic layer 13 of solarcells, a filler layer 14 and a back surface protective sheet 15 in thatorder in a superposed structure with the deposited inorganic oxide thinfilm 2 of the front surface protective sheet A facing inside, andsubjecting the superposed structure to a generally known formingprocess, such as a lamination process, in which those component layersof the superposed structure are brought into close contact by vacuum andare bonded together by hot pressing.

The foregoing protective sheets in accordance with the present inventionand the foregoing solar battery module employing those protective sheetsare examples intended to illustrate the invention and not to beconstrued to limit the scope of the invention.

For example, the foregoing solar battery modules may comprise additionallayers for sunlight absorption, reinforcement or the like.

The soil-resistant layer 303 included in the front surface protectivesheet in accordance with the present invention and the solar batterymodule is a coating film of a composite material containingphotocatalytic powder containing titanium oxide as a principal componentor a sol containing fine particles.

A solvent, aqueous or emulsion composite material containing aphotocatalytic powder for forming the coating film is prepared bypreparing a mixture of one or some kinds of photocatalytic powder, oneor some kinds of bonding agents as a vehicle, when necessary, additivesfor the improvement or modification of the workability, heat resistance,light resistance, water resistance, weather resistance, mechanical orchemical properties, dimensional stability, oxidation resistance,slipperiness, releasability, flame retardancy, antifungal property,electric properties and the like, such as a lubricant, a crosslinkingagent, an oxidation inhibitor, an ultraviolet absorber, a lightstabilizer, a filler, a reinforcing material, a stiffener, an antistaticagent, a flame retarder, a flame-resistant agent, a foaming agent, anantifungus agent, a pigment and the like, a solvent, and a diluent, andkneading the mixture. The concentration of each of the ingredients isdetermined so that the ingredients may not affect sunlighttransmittance. The coating film is formed by spreading the compositematerial by, for example, any one of coating processes including afloating-knife coating process, a knife-over-roll coating process, aninverted knife coating process, a squeeze roll coating process, areverse roll coating process, a roll coating process, a gravure rollcoating process, a kiss-roll coating process, an air blade coatingprocess, an extrusion coating process, a curtain-flow coating processand the like, or any one of printing processes including a gravureprinting process, an offset printing process, a silk-screen printingprocess, a transfer printing process and the like.

The desirable thickness of the coating film as dried is in the range of0.1 to 10 g/m², more preferably, in the range of 0.5 to 1 g/m².

The photocatalytic powder may be a chemical substance having functionsto promote the degradation, destruction, decomposition or reduction inmolecular weight of a resin due to oxidation or the like caused by theoperation of light, such as sunlight, and to facilitate keeping thesurface of the soil-resistant layer clean by destroying the adhesion ofdust to the surface of the soil-resistant layer and enabling wind andrain to remove dust from the surface of the soil-resistant layer.

The photocatalytic powder may be powder of any one of, for example,TiO₂. ZnO, SrTiO₃, CdS, CaP, InP, GaAs, BaTiO₂, K₂TiO₃, K₂NbO₃, Fe₂)₃,Ta₂O₃, WO₃, SnO₂, Bi₂O₅, NiO, Cu₂O, SiC, SiO₂, MoS₂, InPb, RuO₂, CeO₂and the like, any one of metals including Pt, Rh, RuO₂, Nb, Cu, Sn, Niand Fe, or any one of composite material prepared by mixing one or someof those metals and/or one or some of those metal oxides.

The photocatalytic powder content of the composite material is dependenton the shape and density of particles and a preferable photocatalyticpowder content is in the range of about 0.1 to about 30% by weight.

A bonding agent capable of forming a film, excellent in lightresistance, heat resistance, water resistance and the like, capable ofincreasing the hardness of the coating film, excellent in scratchresistance and abrasion resistance and immune to the effect of thephotoactivity of the photocatalytic powder may e used as the vehicle.Possible materials for use as the bonding agent are, for example,polyethylene resins, polypropylene resins, ethylene-vinyl acetatecopolymers, ionomers, ethylene-ethyl acrylate copolymers,ethylene-acrylate or methacrylate copolymers, methyl pentene polymers,polybutene resins, polyvinyl chloride resins, polyvinyl acetate resins,vinyl chloride-vinylidene chloride copolymers, poly(meta)acrylic resins,polyacrylonitrile resins, polystyrene resins, acrylonitrile-styrenecopolymers (AS resins), Acrylonitrile-butadiene-styrene copolymers (ABSresins), polyester resins, polyamide resins, polycarbonate resins,polyvinyl alcohol resins, saponified ethylene-vinyl acetate copolymers,fluorocarbon resins, diene resins, polyacetal resins, polyurethaneresins, epoxy resins, phenolic resins, amino resins, silicone resins,nitrocellulose, inorganic polymers and the like, modified resins, and amixture of some of those resins.

It is particularly preferable to use one or some of low-melting glass,alkali metal silicates, phosphates, colloidal silica and inorganicpolymers among those bonding agents immune to the influence of thephotocatalytic powder.

According to the present invention, an activity blocking layer 303 a(FIG. 26) may be interposed between the soil-resistant layer 303 and theultraviolet absorbing layer or the fluorocarbon resin sheet underlyingthe soil-resistant sheet 303 to prevent the degradation, decompositionor destruction of the ultraviolet absorbing layer or the fluorocarbonresin sheet due to the influence of the photoactivity of thephotocatalytic powder contained in the soil-resistant layer 303.Generally, the activity blocking layer 303 a is formed under thesoil-resistant layer.

A transparent, deposited inorganic oxide thin film, such as a depositedsilicon oxide thin film or a deposited aluminum oxide thin film, may beused as the activity blocking layer 303 a.

The deposited inorganic oxide thin film that serves as the activityblocking layer can be formed by the foregoing film forming process. thethickness of the deposited inorganic oxide thin film is in the range ofabout 100 to about 3000 Å, preferably, in the range of 100 to 1500 Å.

When necessary, a bonding primer layer or the like may be used forforming the coating film of a Composite material containingphotocatalytic powder and serving as the soil-resistant layer 303 toenhance the adhesion of the soil-resistant layer 303 to the underlyinglayer.

The bonding promer layer may be formed of, for example, a materialcapable of froming an inorganic primer layer that will not be decomposedby the photoactivity of the photocatalytic powder contained in thesoil-resistant layer. Representative materials suitable for forming theprimer layer are alkyl titanates including tetraisopropyl titanate,tetrabutyl titanate and tetrastraryl titanate, a product obtainedthrough the hydrolysis of titanium chelate, and inorganic polysilazane(perhydropolysilazane).

In the present invention, tetraisopropyl titanate tetrabutyl titanateare particularly preferable because they are hydrolyzed very quickly andcan be decomposed after forming a coating.

Description will be given of the ultraviolet absorbing layer 304 of thefront surface protective sheet in accordance with the present inventionfor a solar battery module, and the solar battery module. A solvent,aqueous or emulsion composite material for forming the ultravioletabsorbing layer 304 is prepared by preparing a mixture of one or somekinds of ultraviolet absorbers, one or some kinds of bonding agents as avehicle photocatialytic powder, one or some kinds of bonding agents as avehicle and, when necessary, additives for the improvement ormodification of the workability heat resistance, light resistance, waterresistance, weather resistance, mechanical or chemical properties,dimensional stability, oxidation resistance, slipperiness,releasability, flame retardancy, antifungal property, electricproperties and the like, such as one or some of a lubricant, acrosslinking agent, an oxidation inhibitor, a stabilizer, a filler, areinforcing material, a stiffener, an antistatic agent, a flameretarder, a flame-resistant agent, a foaming agent, an antifungus agent,a pigment and the like, a solvent, and a diluent, and kneading themixture. The concentration of each of the ingredients is determined sothat the ingredients may not affect sunlight transmittance. The coatingfilm is formed by spreading the composite material by, for example, anyone of coating processes including a floating-knife coating process, aknife-over-roll coating process, an inverted knife coating process, asqueeze roll coating process, a reverse roll coating process, a rollcoating process, a gravure roll coating process, a kiss-roll coatingprocess, an air blade coating process, an extrusion coating process, acurtain-flow coating process and the like, or any one of printingprocesses including a gravure printing process, an offset printingprocess, a silk-screen printing process, a transfer printing process andthe like.

The desirable thickness of the coating film as dried is in the range of0.1 to 10 g/m², more preferably, in the range of 0.5 to 1 g/m².

The ultraviolet absorber absorbs detrimental ultraviolet rays containedin sunlight, converts the energy of ultraviolet rays into harmlessthermal energy in its molecules to prevent active species that startsthe photodeterioration of polymers from being excited. One or some ofultraviolet absorbers, such as those of a benzophenone group, abenzotriazole group, a salicylate group, an acrylonitrile group,metallic complex salts, a hindered amine group and an inorganicultraviolet absorber, such as ultrafine titanium oxide powder (particlesize: 0.01 to 0.06 μm) or ultrafine zinc oxide powder (particle size:0.01 to 0.04 μm), may be used.

The ultraviolet absorber content of the composite material is dependenton the shape and density of the particles and a preferable ultravioletabsorber content is in the range of about 0.1 to about 20% by weight.

The bonding agent used for preparing the composite material for formingthe coating film serving as the dust-resistant layer and containing thephotocatalytic powder may be used as the bonding agent serving as avehicle.

EXAMPLES

Examples of the sixth embodiment will be described hereinafter.

Example 1

(1) A roll of a 50 μm thick polyvinyl fluoride sheet (PVF sheet), i.e.,base sheet, was mounted on a feed roll of a continuous vacuumevaporation system. The polyvinyl fluoride sheet was unwound and woundaround a coating drum and a 300 Å thick deposited aluminum oxide thinfilm was deposited on a treated surface of the polyvinyl fluoride sheettreated for adhesion improvement by a reactive vacuum evaporationprocess of an electron beam (EB) heating system to form a coatedpolyvinyl fluoride sheet. Aluminum was used as an evaporation source andoxygen gas was supplied to the continuous vacuum evaporation system.

Deposition conditions:

Evaporation source: Aluminum

Vacuum in vacuum chamber: 7.5×10⁻⁶ mbar

Vacuum in deposition chamber: 2.1×10⁻⁶ mbar

EB power: 40 kW

Sheet moving speed: 600 m/min

(2) The 300 Å thick deposited aluminum oxide thin film of the coatedpolyvinyl fluoride sheet was subjected to a glow-discharge plasmaprocess to form a plasma-processed surface. The glow-discharge plasmaprocess was carried out by a glow-discharge plasma producing apparatusof 1500 W in plasma output immediately after the deposition of the 300 Åthick deposited aluminum oxide thin film. In the glow-discharge plasmaprocess, an oxygen/argon mixed gas of 19/1 in O₂/Ar ratio was suppliedso that the pressure of the oxygen/argon mixed gas is maintained at6×10⁻⁵ torr and the processing speed was 420 m/min.

An ultraviolet absorbing layer was formed in the plasma-processedsurface of the deposited aluminum oxide thin film to complete a frontsurface protective sheet in accordance with the present invention. Theultraviolet absorbing layer was formed by coating the plasma-processedsurface of the deposited aluminum oxide thin film with an ultravioletabsorber composite material containing 5 parts by weight of ultrafinetitanium oxide powder of 0.03 μm in particle size and 95 parts by weightof an ethylene-vinyl alcohol copolymer solution (30% solid content)in acoating rate of 0.5 g/m² (dry state) by a gravure coating process.

(3) A solar battery module in accordance with the present invention wasfabricated by using the front surface protective sheet thus fabricated.The front surface protective sheet and a 38 μm thick biaxially orientedpolyethylene terephthalate film provided with an array of amorphoussilicon solar cells were superposed with the plasma-processed depositedaluminum oxide thin film facing inside and with the surface of the 38 μmthick biaxially oriented polyethylene terephthalate film provided withthe array of amorphous silicon solar cells facing the front surfaceprotective sheet. Those component layers were laminated by using anadhesive layer of an acrylic resin to complete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 2

(1) A roll of a 50 μm thick polyvinyl fluoride film (PVF film), i.e.,base sheet, was mounted on a feed roll of a plasma chemical vapordeposition system. A 300 Å thick deposited silicon oxide thin film wasdeposited on a treated surface of the polyvinyl fluoride film treatedfor adhesion improvement under the following conditions to form a coatedpolyvinyl fluoride sheet.

Deposition conditions:

Reaction gas mixing ratio: Hexamethyldisiloxane/oxygen/helium=1/10/10(Unit: slm)

Vacuum in vacuum chamber: 5.0×10⁻⁶ mbar

Vacuum in deposition chamber: 6.0×10⁻⁶ mbar

Power supplied to cooling electrode drum: 20 kW

Film moving speed: 80 m/min

Surface for vapor deposition: Corona-processed surface

(2) The 300 Å thick deposited silicon oxide thin film of the coatedpolyvinyl fluoride film was subjected to a corona discharge process toform a corona-processed surface and to increase the surface tension ofthe deposited silicon oxide thin film from 35 dyne to 60 dyne. Coronadischarge power was 10 kW and the sheet was moved at a moving speed of100 m/min.

An ultraviolet absorbing layer was formed on the corona-processedsurface of the deposited silicon oxide thin film to complete a frontsurface protective sheet in accordance with the present invention. Theultraviolet absorbing layer was formed by coating the corona-processedsurface of the deposited silicon oxide thin film with an ultravioletabsorber composite material containing 1 part by weight of abenzophenone ultraviolet absorber and 99 parts by weight of athermosetting acrylic resin solution (30% solid content)in a coatingrate of 2 g/m² (dry state) by a gravure coating process.

(3) A solar battery module was fabricated by using the front surfaceprotective sheet thus fabricated. The front surface protective sheet anda 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells were superposedwith the corona-processed deposited silicon oxide thin film facinginside and with the surface of the 38 μm thick biaxially orientedpolyethylene terephthalate film provided with the array of amorphoussilicon solar cells facing the front surface protective sheet. Thosecomponent layers were laminated by using adhesive layers of an acrylicresin to complete a solar battery module.

(4) Another protective sheet in accordance with the present inventionand another solar battery module of the same components were fabricatedby the same processes, except that a 50 μm thick fluorocarbon resinsheet of an ethylene-tetrafluoroethylene copolymer (ETFE) was usedinstead of the 50 μm thick polyvinyl fluoride sheet (PVF sheet).

Example 3

(1) A front surface protecting sheet in accordance with the presentinvention was fabricated by the same processes as those in (2) ofExample 1, except that, after forming the ultraviolet absorber layer onthe plasma-processed surface of the deposited aluminum oxide thin filmin (2) of Example 1, a soil-resistant layer of 1 g/m² (dry state) incoating rate was formed on the outer surface of the 50 μm thickpolyvinyl fluoride film as a base sheet by spreading a photocatalyticcomposite material containing 10 parts by weight of ultrafine titaniumoxide powder of 0.03 μm in particle size and 90 parts by weight of atetraethoxysilane solution (20% solid content) by a gravure roll coatingprocess.

A solar battery module provided with the front surface protective sheetthus fabricated was fabricated by the same process as that in Example 1.

Example 4

(1) A front surface protecting sheet in accordance with the presentinvention was fabricated by the same processes as those in (2) ofExample 2, except that, after forming the ultraviolet absorber layer onthe corona-processed surface of the deposited silicon oxide thin film in(2) of Example 2, a soil-resistant layer of 1 g/m² (dry state) incoating rate was formed on the outer surface of the 50 μm thickpolyvinyl fluoride film as a base sheet by spreading a photocatalyticcomposite material containing 10 parts by weight of ultrafine titaniumoxide powder of 0.03 μm in particle size and 90 parts by weight of atetraethoxysilane solution (20% solid content) by a gravure roll coatingprocess.

A solar battery module provided with the front surface protective sheetthus fabricated was fabricated by the same process as that in Example 1.

Example 5

A front surface protecting sheet in accordance with the presentinvention was fabricated by the same processes as those in (2) ofExample 1, except that, an ultraviolet absorber layer was formed on asurface of the 50 μm thick polyvinyl fluoride film as a base sheetopposite the surface of the same on which the deposited aluminum oxidethin film was formed by the same process as that in Example 1 in (2) ofExample 1 instead of forming the same on the plasma-processed surface ofthe deposited aluminum oxide thin film, and a soil-resistant layer of 1g/m² (dry state) in coating rate was formed on the outer surface of the50 μm thick polyvinyl fluoride film by spreading a photocatalyticcomposite material containing 10 parts by weight of ultrafinetitaniumoxide powder of 0.03 μm in particle size and 90 parts by weightof a tetraethoxysilane solution (20% solid content) by a gravure rollcoating process.

A solar battery module provided with the front surface protective sheetthus fabricated was fabricated by the same process as that in Example 1.

COMPARATIVE EXAMPLE 1

(1) A solar battery module was fabricated by superposing a 50 μm thickpolyvinyl fluoride film (PVF film) as a base sheet and a 38 μm thickbiaxially oriented polyethylene terephthalate film provided with anarray of amorphous silicon solar cells with the surface of the 38 μmthick polyethylene terephthalate film provided with the array ofamorphous silicon solar cells facing the front surface protective sheet,and laminating those component layers by using adhesive layers of anacrylic resin.

COMPARATIVE EXAMPLE 2

A solar battery module was fabricated by superposing a 50 μm thickfluorocarbon resin sheet of anethylene-polytetrafluoroethylene copolymerfilm (ETFE film) as a base sheet, as a front surface protective sheetand a 38 μm thick biaxially oriented polyethylene terephthalate filmprovided with an array of amorphous silicon solar cells with the surfaceof the 38 μm thick polyethylene terephthalate film provided with thearray of amorphous silicon solar cells facing the front surfaceprotective sheet, and laminating those component layers by usingadhesive layers of an acrylic resin.

EXPERIMENTS

The protective sheets in Examples 1 to 5 of the present invention andthose in Comparative examples 1 and 2 were subjected to totaltransmittance measurement. The solar battery modules in Examples 1 to 5and Comparative examples 1 and 2 were subjected to solar battery moduleevaluation tests.

(1) Total Transmittance Measurement

Total transmittance (%) of each of the protective sheets in Examples 1to 5 and Comparative examples 1 and 2 against the total transmittance ofthe base sheet as a reference total transmittance was measured by acolor computer.

(2) Solar Battery Module Evaluation Tests

The solar battery modules were subjected to environmental tests inconformity to conditions specified in JIS C8917-1989. Photovoltaicoutput of the solar battery modules was measured before and afterenvironmental tests.

(3) Moisture Permeability and Oxygen Permeability

The moisture permeabilities of the protective sheets in Examples 1 to 5and Comparative examples 1 and 2 were measured in an atmosphere of 40°C. and 90% RH by a moisture permeability measuring apparatus (PERMATRAN,MOCON, USA). The oxygen permeabilities of the protective sheets inExamples 1 to 5 and Comparative examples 1 and 2 were measured in anatmosphere of 23° C. and 90% RH by an oxygen permeability measuringapparatus (OXTRAN, MOCON, USA).

Measured data is tabulated in Table 6-1.

TABLE 6-1 Total Moisture Oxygen Output trans- permea- permea- reductionmittance bility bility ratio (%) (g/m²/24 hr) (cc/m²/24 hr/atm) (%)Example 1 92 0.8 1.4 4 Example 2 93 0.5 1.0 2 Example 3 90 0.8 1.4 3Example 4 91 0.5 1.0 2 Example 5 92 0.8 1.4 4 Comparative 93 26.3 27.715  Example 1 Comparative 95 11.2 ≧500 14  Example 2

In table 6-1, moisture permeability is expressed in a unit ofg/m²/day·40° C.·100% RH, and oxygen permeability is expressed in a unitof cc/m²/day·23° C.·90% RH.

As obvious from Table 6-1, the protective sheets in Examples 1 to 5 havehigh total transmittances, respectively, and are excellent in moistureimpermeability and oxygen impermeability.

The output reduction ratios of the solar battery modules employing theprotective sheets in Examples 1 to 55 were low.

The protective sheets in Comparative examples 1 and 2 had high totaltransmittances, respectively. However, the moisture impermeabilities andthe oxygen impermeabilities of the protective sheets in Comparativeexamples 1 and 2 were low. Consequently, the output reduction ratios ofthe solar battery modules employing the protective sheets in Comparativeexamples 1 and 2 were high.

As apparent from the foregoing description, the present invention takesinto consideration the characteristics of a glass sheet that is used asthe front surface protective sheet of a solar battery module,photocatalytic powder and an ultraviolet absorber, uses a fluorocarbonresin sheet as a base sheet, fabricates a coated fluorocarbon resinsheet by forming a transparent, vitreous deposited inorganic oxide thinfilm, such as a silicon oxide thin film or an aluminum oxide thin film,on one of the surfaces of the fluorocarbon resin sheet, and fabricates aprotective sheet for a solar battery module by forming a soil-resistantlayer of a composite material containing a photocatalytic powder and/oran ultraviolet absorbing layer of a composite material containing anultraviolet absorber on one of or both the surfaces of the fluorocarbonresin sheet, and forms a solar battery module by using the protectivesheet as a front surface protective sheet by superposing the protectivesheet as a front surface protective sheet, a filler layer, a filmprovided with solar cells, i.e., photovoltaic cells, a filler layer anda back surface protective sheet in that order in a superposed structurewith the deposited inorganic oxide thin film facing inside, bringing thecomponent layers of the superposed structure into close contact byvacuum and bonding together those component layers by a laminationprocess using hot pressing. The protective sheet has greatly improvedmoisture resistance to prevent the permeation of moisture and oxygenthrough the protective sheet, is excellent in light resistance, heatresistance and water resistance, limits performance degradation due toaging to the least extent, is excellent in protective ability, preventssoiling of its surface by accumulated dust, can be fabricated at a lowcost and can be used for the fabrication of a low-cost, safe solarbattery module.

The materials mentioned in the description of the first, the second, thethird, the fourth and the fifth embodiment are applicable to the sixthembodiment.

SEVENTH EMBODIMENT

A protective sheet (cover film) in a seventh embodiment according to thepresent invention is used as the front or the back surface protectivesheet of a solar battery module and comprises at least a base film(weather-resistant sheet), an ultraviolet intercepting layer, aninfrared intercepting layer or a highly reflective layer formed on thebase film.

The protective sheet in the seventh embodiment of the foregoingconstruction has the following effects.

(1) The protective sheet is a laminated film comprising at least a basefilm and one or some of an ultraviolet intercepting layer, an infraredintercepting layer and a highly reflective layer. The protective sheetis capable of intercepting some types of light radiation withwavelengths that do not contribute to power generation, such asultraviolet radiation and infrared radiation to prevent the degradationof solar cells attributable to the effect of those types of lightradiation. The use of a laminated film formed by laminating a base filmand a highly reflective layer as a back surface protective sheetdisposed on the back side of solar cells improves power generatingefficiency.

(2) The protective sheet (cover film) for a solar battery module can beproduced at a high productivity by forming an ultraviolet interceptinglayer, an infrared intercepting layer and a highly reflective layer on along, wide base film by a continuous coating means or evaporation means.

(3) A glass sheet serving as the front surface protective sheet of asolar battery module can be replaced with the protective sheet (coverfilm) of the present invention. The protective sheet of the presentinvention is easy to handle, improves the productivity of a productionline for producing solar battery modules, enables the formation of asolar battery module in lightweight construction at a reduced cost.

The ultraviolet intercepting layer is a coating resin film containingdispersed metal oxide particles of a mean particle size in the range of1 to 1000 nm.

Since the coating resin film containing disperse metal oxide particlesis capable of satisfactorily intercepting ultraviolet radiation, theprotective sheet (cover film) has a satisfactory ultravioletintercepting ability.

Accordingly, the ultraviolet degradation of the solar battery can beprevented by covering the solar cells with the protective sheet.

The metal oxide particles are those of TiO₂, ZnO, α-Fe₂O₃ or CeO₂.

Since the coating resin film containing the dispersed metal oxideparticles is excellent in ultraviolet intercepting ability andstability, the protective sheet has an excellent ultravioletintercepting ability.

The ultraviolet degradation of a solar battery can be suppressed for along period of use by covering the solar cells of the solar battery withthe protective sheet.

The infrared intercepting layer is a deposited metal film or a coatingresin film containing dispersed metal oxide particles.

Since the deposited metal film or the coating resin film containing thedisperse metal oxide particles has a satisfactory infrared interceptingability, the protective sheet for a solar battery module has asatisfactory infrared intercepting ability.

Accordingly, the infrared degradation (heat degradation) of a solarbattery can be prevented by covering the solar cells of the solarbattery with the protective sheet (cover film).

The deposited metal film is a deposited film of Al or Ag.

Since the deposited film of Al or Ag is excellent in infraredintercepting ability and long-term stability, the protective sheet hasan excellent infrared intercepting ability.

Accordingly, the infrared degradation of a solar battery can beprevented for a long period of use by covering the solar cells of thesolar battery with the protective sheet (cover film).

The deposited metal film intercepts visible radiation if the same isexcessively thick. Therefore, it is preferable to incorporate thedeposited metal film into a protective sheet for use as a back surfaceprotective sheet.

The metal oxide particles are those of SnO₂ capable of efficientlyabsorbing infrared radiation.

Since the coating resin film containing dispersed SnO₂ particles iscapable of efficiently intercepting infrared radiation and excellent inlong-term stability, the protective sheet including the coating resinfilm containing dispersed SnO₂ particles has an excellent infraredintercepting ability.

Accordingly, the infrared degradation of a solar battery can beprevented for a long period of use by covering the solar cells of thesolar battery with the protective sheet (cover film).

The highly reflective layer is a deposited Ag or Al film or a resin filmcontaining a dispersed white pigment.

The resin film containing the dispersed white pigment may be a whitefilm formed by spreading a mixture of a weather-resistant resin, such asa fluorocarbon resin or a highly weather-resistant polyethyleneterephthalate resin, and a white pigment or a weather-resistant filmformed by coating a weather-resistant film, such as a fluorocarbon resinfilm or a highly weather-resistant biaxially oriented polyethyleneterephthalate film (hereinafter referred to as “PET film”), with a whiteresin film formed by applying a liquid resin containing a dispersedwhite pigment in a film to the weather-resistant film and drying thefilm.

Since the deposited Ag or Al film or the resin film containing thedispersed white pigment is highly reflective, the protective sheet has ahigh light reflecting ability.

Accordingly, a solar battery module provided with the protective sheetbonded to the back surface of a photovoltaic layer provided with solarcells reflects part of incident light fallen on the front surface of thesolar battery module and penetrated the solar cells toward the solarcells, which improves the power generating efficiency of the solarbattery module.

A protective sheet fabricating method in accordance with the presentinvention fabricates a protective sheet for a solar battery module. Theprotective sheet comprises a laminated film at least comprising aweather-resistant sheet (base film) and an ultraviolet interceptinglayer formed on the base film. The ultraviolet intercepting layer isformed by applying a liquid resin containing dispersed TiO₂ or CeO₂particles having a mean particle size in the range of 1 to 1000 nm in afilm to the base film and drying the film.

The protective sheet (cover film) for a solar battery module providedwith an ultraviolet intercepting layer can be produced at a highproductivity and low cost by forming an ultraviolet intercepting layeron a long, wide base film moving at a high moving speed on a continuouscoating means.

A protective sheet fabricating method in accordance with the presentinvention may form a coating primer layer on a surface of the base filmon which the liquid resin containing dispersed TiO₂ or CeO₂ particles isto be applied.

Thus, the base film of the protective sheet and the coating resin filmcontaining dispersed TiO₂ or CeO₂ particles can firmly bonded together.

Even if a solar battery module provided with the protective sheet inaccordance with the present invention is used under severe outdoorconditions, the ultraviolet intercepting layer will not come off thebase film and solar battery module has improved stability.

A protective sheet fabricating method in accordance with the presentinvention fabricates a protective sheet for a solar battery module. Theprotective sheet comprises a laminated film at least comprising aweather-resistant sheet (base film) and an infrared intercepting layerformed on the base film. The infrared intercepting layer is a depositedmetal film deposited on the base film or a coating resin film formed byapplying a liquid resin containing dispersed metal oxide particles in afilm to the base film and drying the film.

The protective sheet (cover film) for a solar battery module providedwith an infrared intercepting layer can be produced at a highproductivity and low cost by forming an infrared intercepting layer on along, wide base film moving at a high moving speed on a continuousdeposition or coating means.

A solar battery module in accordance with the present invention isprovided with the protective sheet bonded to the front surface of alayer provided with solar cells by a heat-adhesive filler layer.

The heat-adhesive filer layer may be formed of a heat-adhesive resincontaining as a principal component, for example, an ethylene-vinylacetate copolymer, a polyolefin resin, a polyvinyl butyral resin or asilicone resin.

The solar cells can be embedded in the heat-adhesive filler layer in astable state, and can be sandwiched between the protective sheetexcellent in ultraviolet intercepting ability, infrared interceptingability and light reflecting ability. Consequently, ultraviolet andinfrared radiation which does not contribute to power generation can beintercepted, the highly reflective layer disposed behind the solar cellsimproves power generating efficiency, and the solar battery module isexcellent in durability and generates power at a high power generatingefficiency.

Protective sheets (cover films) in the seventh embodiment for a solarbattery module and solar battery modules employing the protective sheetswill be described with reference to the accompanying drawings.

The present invention is not limited in its practical application tothose shown in the drawings.

FIGS. 30 to 33 are typical sectional views of examples of protectivesheets in the seventh embodiment for solar battery modules.

Referring to FIG. 30, a protective sheet 410 in a first example of theseventh embodiment of the present invention for a solar battery modulecomprises at least a base film 401 (weather-resistant sheet) 401 and anultraviolet intercepting layer 402 formed on one of the surfaces of thebase film 401.

Preferably, the base film 401 is a durable film excellent in weatherresistance, strength and resistances to detrimental effects, such as apolyvinyl fluoride film (hereinafter referred to as “PVF film”), afluorocarbon resin film, such as an ethylene-tetrafluoroethylenecopolymer film (hereinafter referred to as “ETFE film”), a highlyweather-resistant biaxially oriented polyethylene terephthalate film(hereinafter referred to as “weather-resistant PET film”), apolycarbonate film or a polyacrylate film.

The ultraviolet intercepting layer 402 may be a coating resin filmcontaining dispersed metal oxide particles having a mean particle sizein the range of 1 to 1000 nm. Preferable metal oxide particles areparticles of TiO₂, ZnO, α-Fe₂O₃ or CeO₂. TiO₂ or CeO₂ particles areparticularly preferable.

Particles of one of those metal oxides or a mixture of some of thosemetal oxides may be used.

An acrylic resin or a silicone resin may be used as a binder for holdingthe particles together. An additive, such as a crosslinking agent or asilane coupling agent may be added to the resin to enhance the weatherresistance of the resin.

A primer layer 402 a of a polyisocyanate primer or a polyacryamineprimer may be formed on a surface of the base film 401 on which theultraviolet intercepting layer 40 is to be formed to enhance adhesionbetween the base film 401 and the ultraviolet intercepting layer 402before forming the ultraviolet intercepting layer 402 on the base filmby a coating process.

The protective film 401 intercepts ultraviolet radiation and transmitsvisible radiation. In most cases, the protective sheet is used as afront surface protective sheet to be disposed on the light receivingside of a solar battery module.

Referring to FIG. 31, a protective sheet 420 in a second example of theseventh embodiment of the present invention for a solar battery modulecomprises at least a base film 401 and an infrared intercepting layer403 formed on a surface of the base film 401.

When necessary, a primer layer 403 a may be sandwiched between the basefilm 401 and the infrared intercepting layer 403 to enhance adhesionbetween the base film 401 and the infrared intercepting layer 403.

The base film 401 may be formed of the same material as the base film401 of the example shown in FIG. 30. The infrared intercepting layer 403may be a coating resin layer containing dispersed metal oxide particles,such as SnO₂ particles.

The same resin as that used for forming the ultraviolet interceptinglayer may be used as a binder for holding the metal oxide particles.

It is preferable that the infrared intercepting layer 403 contains metaloxide particles, such as SnO₂ particles when the protective sheet 420 isused as the front surface protective sheet of a solar battery module. Itis preferable that the infrared intercepting layer 403 is a deposited Alor Ag film when the protective sheet 420 is used as the back surfaceprotective sheet of a solar battery module.

Referring to FIG. 32, a protective sheet 430 in a third example of theseventh embodiment of the present invention for a solar battery modulecomprises at least a base film 401, an ultraviolet intercepting layer402 formed on the base film 401, and an infrared intercepting layer 403formed on the ultraviolet intercepting layer 402.

When necessary, a primer layer 402 a may be sandwiched between the basefilm 402 and the ultraviolet intercepting layer 402, and a primer layer403 a may be sandwiched between the ultraviolet intercepting layer 402and the infrared intercepting layer 403 to enhance adhesion between thecontiguous layers. When the infrared intercepting layer 403 is adeposited metal film, a primer for deposited metal film may be used.

Materials forming the base film 401, the ultraviolet intercepting layer402 and the infrared intercepting layer 403 may be those of the examplesshown in FIGS. 30 and 31 and hence the further description thereof willbe omitted.

When the infrared intercepting layer 403 is a coating resin layercontaining dispersed metal oxide particles, such as SnO₂ particles, theprotective sheet 430 intercepts ultraviolet radiation and infraredradiation and transmits visible radiation. Therefore, the protectivesheet 430 is suitable for use as a front surface protective sheet. Theprotective sheet 430 intercepts visible radiation as well as ultravioletradiation and infrared radiation when the infrared intercepting layer403 is a deposited metal film. Therefore, the protective sheet issuitable for use as a back surface protective sheet.

Referring to FIG. 33, a protective sheet 440 in a fourth example of theseventh embodiment of the present invention for a solar battery modulecomprises at least a base film 401′ and a highly reflective layer 404formed on the base film 401′.

When necessary, a primer layer may be sandwiched between the base film401′ and the highly reflective layer 404 to enhance adhesion between thebase film 401′ and the highly reflective layer 404.

The base film 401′ may be the same as the base films 402 of theprotective sheet shown in FIGS. 30 to 32. A highly reflective depositedAg or Al film or a resin film containing dispersed white pigment isparticularly suitable for use as the highly reflective layer 404.

The protective sheet 440 thus constructed is used as the back surfaceprotective sheet of a solar battery module. Part of incident lightfallen on the front surface of the solar battery module and penetratedthe solar cells is reflected toward the solar cells, which improves thepower generating efficiency of the solar battery module.

When necessary, each of the protective sheets shown in FIGS. 30 to 34for solar battery modules may additionally be provided with, forexample, a deposited inorganic oxide film, such as an aluminum oxidefilm or a silicon oxide film (SiOx film), or each of the layers formedon the base films may be coated with a protective layer.

Generally, a filler layer is interposed between the front surface of aphotovoltaic layer provided with solar cells and the protective sheetwhen bonding the protective sheet to the photovoltaic layer. If adhesionbetween the protective sheet and the filler layer is not high enough, anadhesive layer may be formed on a surface of the protective sheet to bebonded to the photovoltaic layer.

Referring to FIG. 34 showing a solar battery module in a typicalsectional view, protective sheets in accordance with the presentinvention are bonded to the front and the back surface of a photovoltaiclayer provided with solar cells.

A solar battery module 400 shown in FIG. 34 is formed by superposing,from the front side toward the back side, a base film 401, anultraviolet intercepting layer 402, an infrared intercepting layer 403,a filler layer 405, a photovoltaic layer 406 provided with solar cells,a filler layer 405′, a highly reflective layer 404 and a base film 401′,and laminating those component layers.

The photovoltaic layer 406 is sandwiched between the filler layers 405and 405′, a protective sheet comprising the base film 401, theultraviolet intercepting layer 402 and the infrared intercepting layer403 is bonded to the front surface of the photovoltaic layer 406, and aprotective sheet comprising the base film 401′ and the highly reflectivesheet 404 is bonded to the back surface of the photovoltaic layer 406.

Therefore, ultraviolet radiation and infrared radiation that do notcontribute to power generation and promotess the degradation of solarcells are intercepted by the protective sheet and, consequently, thedegradation of the solar cells is prevented and the durability of thesolar battery module is improved.

Visible radiation that contributes to power generation travels throughthe front protective sheet and falls on the solar cells to cause thesolar cells to generate power. Part of visible radiation penetrated thephotovoltaic layer 406 is reflected by the highly relfective layer 404so as to fall again on the solar cells, so that visible radiation isused effectively for power generation and the efficiency ofphotoelectric conversion is improved.

EXAMPLES

Examples of the seventh embodiment will be described hereinafter.

Example 1

A front surface protective sheet for a solar battery module comprises a70 μm thick highly weather-resistant PET film, and an infraredintercepting layer of an acrylic resin containing dispersed SnO₂particles formed on one surface of the PET film. A back surfaceprotective sheet is a laminated film formed by superposing a 38 μm thickPVF film, a 50 μm thick aluminum foil and a 38 μm thick PVF film in thatorder and laminating those component layers by a dry lamination process.A solar battery module in Example 1 was fabricated by bonding the frontsurface protective sheet and the back surface protective sheet to thefront and the back surface, respectively, of a photovoltaic layerprovided with an array of crystal silicon solar cells with 500 μm thickethylene-vinyl acetate copolymer films, i.e., heat-adhesive fillerlayers, by a vacuum lamination process.

Example 2

A solar battery module in Example 2 was fabricated by using the samecomponents as those of the solar battery module in Example 1 by the sameprocesses as in Example 1, except that a front surface protective sheetcomprising a 70 μm thick highly weather-resistant PET film, anultraviolet intercepting layer of an acrylic resin containing dispersedTiO₂ particles having a mean particle size of 10 nm formed on the PETfilm, and an infrared intercepting layer of an acrylic resin containingdispersed SnO₂ particles was used instead of the front surfaceprotective sheet of Example 1.

Example 3

A solar battery module in Example 3 was fabricated by using the samecomponents as those of the solar battery module in Example 1 by the sameprocesses as in Example 1, except that a front surface protective sheetcomprising a 70 μm thick highly weather-resistant PET film and anultraviolet intercepting layer of an acrylic resin containing dispersedTiO₂ particles having a mean particle size of 10 nm formed on the PETfilm was used instead of the front surface protective sheet of Example1.

Example 4

A solar battery module in Example 4 was fabricated by using the samecomponents as those of the solar battery module in Example 1 by the sameprocesses as in Example 1, except that a front surface protective sheetsimilar to that in Example 2 and comprising a 70 μm thick highlyweather-resistant PET film, an ultraviolet intercepting layer of anacrylic resin containing dispersed TiO₂ particles having a mean particlesize of 10 nm formed on the PET film, and an infrared intercepting layerof an acrylic resin containing dispersed SnO₂ particles formed on theultraviolet intercepting layer was used instead of the front surfaceprotective sheet of Example 1, and a back surface protective sheetcomprising a 70 μm thick highly weather-resistant PET film, and a backsurface protective sheet comprising a 70 μm thick highlyweather-resistant PET film and an 800 Å thick deposited Al film formedas a highly reflective layer on the PET film was used instead of theback surface protective sheet of Example 1.

COMPARATIVE EXAMPLE 1

A solar battery module in Comparative example 1 was fabricated by usingthe same components as those of the solar battery module in Example 1 bythe same processes as in Example 1, except that a 70 μm thick highlyweather-resistant PET film not provided with any infrared interceptinglayer was used as a front surface protective sheet.

Evaluation of Solar Battery Modules in Examples 1 to 4 and ComparativeExample 1

The solar battery modules in Examples 1 to 4 and Comparative example 1were subjected to tests to evaluate their performance and long-termreliability, in which photoelectric conversion efficiency η (%) and fillfactor (FF) were measured in an initial state and in a state afterirradiation with 1 sun, for 2000 hr. Measured data is tabulated in Table7-1.

TABLE 7-1 Characteristic of solar battery State after exposure Initialstate to 1 sun, 2000 hr Conversion Conversion efficiency efficiency η(%) FF η (%) FF Example 1 10.5 0.65 10.2 0.60 Example 2 10.4 0.63 10.10.59 Example 3 10.5 0.66 10.3 0.60 Example 4 11.5 0.70 10.8 0.65Comparative 10.4 0.62 9.5 0.58 Example 4

As obvious from the measured data shown in Tables 7-1, the solar batterymodules in Examples 1 to 4 have conversion efficiencies not smaller than10% in an initial state and in a state after exposure to sunlight for2000 hr, and the initial conversion efficiencies of the solar batterymodules in Examples 1 to 4 were not reduced significantly by sunlightirradiation. The conversion efficiency of the solar battery module inComparative example 1 was reduced to 9.5% by sunlight irradiation, andthe conversion efficiency reduction ratio was large.

As is apparent from the foregoing description, the solar battery modulesof the present invention are excellent in performance and long-termreliability. The protective sheet of the present invention and the solarbattery module provided with the same protective sheet can be fabricatedeasily at a high productivity and are economically advantageous.

The materials mentioned in the description of the first to the sixthembodiment are applicable to the seventh embodiment.

EIGHTH EMBODIMENT

Basic Construction

A protective sheet (film) in an eighth embodiment according to thepresent invention is intended for use as a front surface protectivesheet of a solar battery module for covering the front surface of aphotovoltaic layer provided with solar cells. The protective sheet is asingle weather-resistant sheet (base film) or is a laminated sheetcomprising a plurality of layers including a base film and at least onelight confining layer.

The protective sheet (protective film) for a solar battery module caneffectively be used as a substrate for the photovoltaic layer. Thematerial and thickness of the base film are determined properlyaccording to the use of the protective sheet. A film meetingrequirements for strength, heat resistance, weather resistance,transparency and the like is used as the base film.

The protective sheet in accordance with the present invention for asolar battery module has a function to confine light and hence lightfallen on the solar cells can repeatedly be used, which enhances powergenerating efficiency.

A protective sheet (film) in accordance with the present invention isintended for use as a front surface protective sheet of a solar batterymodule for covering the front surface of a photovoltaic layer providedwith solar cells. The protective sheet is a single weather-resistantsheet (base film) or is a laminated sheet comprising a plurality oflayers including a base film, at least one light confining layer, and anadhesive layer for bonding the protective sheet to a photovoltaic layerprovided with solar cells.

A protective sheet of such laminated construction having a base film, alight confining layer and the adhesive layer for bonding the protectivesheet to a surface of a photovoltaic layer is suitable particularly foruse as a protective sheet for a solar battery module.

When the protective sheet for a solar battery module is thusconstructed, it is not necessary to sandwich an adhesive film providedwith a soft, sticky adhesive layer and difficult to handle between theprotective sheet and the photovoltaic layer provided with solar cells.The adhesive layer need not be formed in a great thickness to facilitatehandling the protective sheet and may be formed in the least necessarythickness. The protective sheet simplifies laminating process andimproves productivity.

When the light confining layer is formed on the adhesive layer, i.e.,when the light confining layer is the innermost layer of the protectivesheet to be brought into contact with the photovoltaic layer, aperipheral portion of the light confining layer is removed so that aperipheral portion of the adhesive layer is exposed, and the protectivesheet can be bonded to the photovoltaic layer with the exposedperipheral portion of the adhesive layer.

According to the present invention, the light confining layer has anirregular surface comprising regularly arranged projections. The heightof the projections or depth of recesses between the projections is inthe range of 0.1 nm to 500 μm.

Preferably, the irregular surface of the light confining layer is formedby arranging ridges or furrows of a triangular, trapezoidal orsemicircular cross section having inclined surfaces, projections orrecesses having the shape of a pyramid, a frustum, a hemisphere, a roundprojection or the like. An irregular surface formed by arrangingpyramidal projections or recesses having intersecting surfaces formingan angle (apex angle) of 90° is particularly preferable.

Preferably, the height or depth of the irregularities is in the range of0.1 nm to 500 μm. When the height or depth of the irregularities is lessthan 0.1 nm or greater than 500 μm, the effect of the light confininglayer to confine light thereto by refracting and reflecting light is nothigh enough.

The appropriate range of the height or depth of the irregularities isdependent on the type of the solar battery module. For example, asuitable range of the height or depth of the irregularities is 0.1 nm to500 nm when thin-film solar cells, such as amorphous silicon solarcells, are employed, and is 1 to 500 μm when thick solar cells, such assingle-crystal silicon solar cells, are employed.

A light confining layer meeting such conditions has a further effectivelight confining function.

According to the present invention, a light confining layer may have anirregular surface having large irregularities of a height or depth inthe range of 1 to 500 μm, and small irregularities of a height or depthin the range of 0.1 to 500 nm formed on the large irregularities.

This light confining layer is capable of further effectively confininglight fallen on the solar cells by effectively refracting and reflectingthe incident light.

At least the base film of the protective sheet for a solar batterymodule is a weather-resistant film.

Thus, the protective sheet has an improved weather resistance. When theprotective sheet is bonded to the front surface of the photovoltaiclayer provided with the solar cells, the power generating performance ofthe solar cells is improved, the solar cells can safely be protected fora long period of use, and the solar battery module has excellentlong-term reliability.

The component layers of the protective sheet for a solar battery modulemay include a gas-barrier layer.

The protective sheet of the present invention is used, in most cases, asa front surface protective sheet for covering the light receifingsurface of a photovoltaic layer provided with solar cells. Therefore, itis preferable that the gas-barrier layer has a high transmittanceparticularly to visible radiation. Preferable layers for use as thegas-barrier layer are deposited layers of, for example, silicon oxide(SiO_(x)), silicon nitride (SiN_(x)), aluminum oxide (Al_(x)O_(y)) andthe like, or inorganic-organic hybrid layers.

The gas-barrier layer improves the gas impermeability, i.e.,impermeability to moisture, oxygen and the like, of the protectivesheet.

Those gas-barrier layers may be used individually or in combination in acomposite layer.

The gas-barrier layer improves the impermeability to moisture, oxygenand the like of the protective sheet, and the protective sheet issuitable for use in combination with polycrystalline or microcrystallinesilicon thin-film solar cells subject to degradation by moisture oroxygen or tandem solar cells comprising, in combination, polycrystallineor microcrystalline silicon thin-film solar cells, and amorphoussilicon, amorphous silicon-germanium or copper-selenium solar cells.

According to the present invention, the protective sheet for a solarbattery module is placed on at least one of the surfaces of aphotovoltaic layer provided with solar cells.

Since the protective sheet in accordance with the present invention isexcellent, as mentioned above, in strength, heat resistance, weatherresistance, transparency and gas impermeability and has a lightconfining function, the incident light can effectively used for powergeneration, and the solar battery module employing the protective sheetof the present invention is excellent in long-term reliability and iscapable of efficiently generating power.

The use of the protective sheet provided with the adhesive layersimplifies the solar battery module fabricating process, and enables thefabrication of a solar battery module excellent in long-termreliability, performance and productivity.

Materials for fabricating protective sheet (protective film) inaccordance with the present invention for solar battery modules andprotective sheet fabricating methods will be described hereinafter.

Preferably, a weather-resistant sheet (base film) for a protective sheetin accordance with the present invention for a solar battery module isexcellent in strength, heat resistance and transparency (transmittanceto visible radiation) as well as in weather resistance. Possible filmsas the base film are, for example, fluorocarbon resins films, such aspolyvinyl fluoride films (PVF films) and ethylene-tetrafluoroethylenecopolymer films (ETFE films), polycarbonate films, polyethersulfonefilms, polysulfone films, polyacrylonitrile films, acrylic resin films,cellulose acetate films, glass-fiber-reinforced polycarbonate films,weather-resistant polyethylene terephthalate films and weather-resistantpolypropylene films.

Those films may be used either individually or in combination incomposite films.

Preferably, the gas-barrier layer formed of a gas-barier material istransparent, heat-resistant and weather-resistant as well as excellentin impermeability. From this point of view, suitable gas-barrier layersare deposited films of one of silicon oxide (SiO_(x)), silicon nitride(SiN_(x)), tin oxide (SnO_(x)) and aluminum oxide (Al_(x)O_(y)),deposited films each of a mixture of some of those metal oxides, orcomposite films each of some of those metal oxides.

The deposited silicon oxide films(SiO_(x) films), silicon nitride films(SiN_(x) films), tin oxide films (SnO_(x) films and aluminum oxide films(Al_(x)O_(y) films can easily be formed by a CVD process, a PE-CVD(plasma-enhanced CVD) process, a PVD process and a sputtering process,respectively, on a base film. The PE-CVD process is particularlypreferable because the same is capable of depositing a dense,transparent deposoted film at a low temperature.

A suitable thickness of the deposited film is in the range of 50 to 5000Å, preferably, in the range of 300 to 1500 Å.

The inorgaic-organic hybrid coating layer may be formed of, for example,tetraethoxysilane and an ethylene-vinyl alcohol copolymer. Coatingliquids of those materials are prepared, and the coating liquids areapplied to the base film in films by a gravure roll coating process orthe like and hot-drying the films.

Preferably, the inorgaic-orgaic hybrid coating layer is formed in acoating rate (dry state) in the range of 0.5 to 8 g/m², more preferably,in the range of 1 to 5 g/m².

The inorganic-organic hybrid coating layer is excellent in gasimpermeability and may be used individually. The inorganic-organichybrid coating layer may be formed on a deposited inorganic oxide filmto enhance the gas impermeability of the deposited inorganic oxide film.

An adhesive layer to be formed beforehand on a protective sheet to bondthe protective sheet to a photovoltaic layer provided with solar cellsmay be formed of any one of ethylene copolymers including ethylene-vinylacetate copolymers, ethylene-acrylate copolymers and ethylene-α-olefincopolymers, linear low-density polyethylene resins (L-LDPE), ionomers,polyvinyl butyral resins, silicone resins, and elastomers includingpolystyrene resins, polyolefine resins, polydiene resins, polyesterresins, polyurethane resins, fluorocarbon resins and polyamide resins.

The ethylene copolymers may be modified ethylene copolymers producedthrough the modification of ethylene copolymers by graftcopolymerization.

There is not particular restrictions on the thickness of the adhesivelayer. The adhesive layer may be formed in a suitable thicknessaccording to the type and shape of the photovoltaic layer provided withsolar cells to which the protective sheet is to be bonded.

The material for forming the adhesive layer may be prepared in, forexample, a solution or a dispersion according to the material and thethickness of the adhesive layer to be formed, and the adhesive layer maybe formed on a surface of the base film by a suitable means, such as acoating process, an extrusion coating process, a calender coatingprocess, a hot lamination process or a dry lamination process.

The light confining layer may be formed, for example, in a shape asshown in FIG. 37(a) or 37(b).

FIGS. 37(a) and 37(b) are typical sectional views of light confininglayers for protective sheets in accordance with the present inventionfor solar battery modules. As shown in FIG. 37(a), a light confininglayer 502 comprises a transparent irregular structure 504 formed on onesurface (lower surface as viewed in FIG. 37(a)) of a base film 501, anda support film 506 provided with an adhesive layer 505, superposed onthe irregular structure 504 with adhesive layer 505 facing the irregularstructure 504 and bonded to the irregular structure 504 at bonding spots510 arranged at predetermined intervals.

Light scattered outward as indicated by the arrows is reflected andrefracted so as to fall again on solar cells.

The base film may be provided with a single light confining layersimilar to the light confining layer 502 as shown in FIG. 37(a), twolight confining layers may be formed on the opposite surface,respectively, of the base film or two light confining layers may beformed on one of surfaces of the base film for satisfactory lightconfining effect.

FIG. 37(b) shows a light confining layer 502 similar to that shown inFIG. 37(a), except that the light confining layer 502 shown in FIG.37(b) has a transparent, composite irregular structure 504 consisting ofa large irregular structure 504 a and a small irregular structure 504 bformed on the surface of the large irregular structure 504 a instead ofthe irregular structure 504 shown in FIG. 37(a).

As mentioned above, it is preferable that each of the irregularstructures 504, 504 a and 504 b is formed by arranging ridges or furrowsof a triangular, trapezoidal or semicircular cross section, projectionsor recesses having the shape of a pyramid, a frustum, a hemisphere, around projection or the like. An irregular structure formed by arrangingpyramidal projections or recesses having intersecting surfaces formingan angle (apex angle) of 90° is particularly preferable.

Preferably, the height or depth of the irregularities is in the range of0.1 nm to 500 μm.

When the irregularities of the irregular structure has a relativelygreat height or depth in the range of 0.1 μm to 500 μm, the irregularstructure can be formed, for example, by heating and softening athermoplastic resin layer formed on the base film, pressing an embossingdie against the softened thermoplastic resin layer and cooling theembossed thermopoastic resin layer. Such an irregular structure can beformed also by applying an ionizing radiation curable resin, such as anultraviolet curable resin, in a resin film to the base film pressing aseparable die or a separable embossing sheet against the film of theionizing radiation curable resin, curing the resin film and separatingthe separable die or the separable embossing sheet from the resin film.

When the irregularities of the irregular structure has a relativelysmall height or depth in the range of 0.1 nm to 0.1 μm, the irregularstructure can be formed, for example, by forming a transparent ZnO oreSnO₂ thin film by a CVD process with etching action or by forming aspecular thin film by a CVD process and forming minute irregularities inthe specular thin film by sputtering.

A transparent SiOx thin film formed by a CVD or a PE-CVD process has anirregular structure having minute projections. The transparent SiO_(x)thin film serves also as a gas-barrier layer.

The irregular structure of each of the light confining layers 502 shownin FIGS. 37(a) and 37(b) has an air layer to enhance light reflectingand refracting effect. A transparent material, such as a transparentresin, having a refractive index different from that of the materialforming the irregular structure or a resin containing dispersedparticles of a transparent material, such as TiO₂ or SiO_(x), having arefractive index different from that of the material forming theirregular structure may be filled in furrows or recesses in theirregular structure to enhance the light reflecting and refractingeffect of the light confining layer.

When the irregular structure is formed of a resin, a material having alarge refractive index in the range of 1.8 to 2.2 or a material having asmall refractive index in the range of 1.1 to 1.3 is suitable as thetransparent material having a refractive index different from that ofthe material forming the irregular structure.

When the irregular structure is formed of a resin, a transparent thinfilm having a refractive index different from that of the materialforming the irregular structure, such as a film of SiO_(x), ZnS, TiO₂ orSb₂O₃, may be formed on the surfaces defining the irregularities of theirregular structure by a deposition means. The transparent thin filmimproves the reflection efficiency of the surface of the irregularitiesto ensure satisfactory light confining effect.

EXAMPLES

Examples of the eighth embodiment will be explained with reference tothe accompanying drawings. The present invention is not limited in itspractical application to examples shown in the drawings.

A protective sheet (film) in accordance with the present invention for asolar battery module is intended to be used as a front protective sheetto be bonded to the front surface of a photovoltaic layer 507 providedwith solar cells. The protective sheet is a single weather-resistantsheet (base film) provided with a light confining layer or a laminatedsheet comprising a plurality of layers including a base film and a lightconfining layer. FIGS. 35(a) to 35(e) show protective sheets inaccordance with the present invention by way of example.

FIGS. 35(a) to 35(e) are typical sectional views of protective sheets(protective films) in accordance with the present invention for solarbattery modules. The protective sheet shown in FIG. 35(a) comprises abase film (weather-resistant sheet) 501 and a light confining layer 502a formed on the outer surface of the base film 501, i.e. a surface onthe light receiving side of the base film 501. The protective sheetshown in FIG. 35(b) comprises a base film (weather-resistant sheet) 501and a light confining layer 502 a formed on the inner surface of thebase film 501, i.e., a surface to be laminated to a photovoltaic layer507 provided with solar cells.

The protective sheet shown in FIG. 35(c) comprises a base film(weather-resistant sheet) 501, a light confining layer 502 a formed onthe outer surface of the base film 501, and a light confining layer 502b formed on the inner surface of the base film 501.

The protective sheets shown in FIG. 35(d) comprises a base film 501, alight confining layer 502 b formed on the outer surface of the base film501, and a light confining layer 502 a formed on the outer surface ofthe light confining layer 502 b. The protective sheets shown in FIG.35(e) comprises a base film 501, a light confining layer 502 a formed onthe inner surface of the base film 501, and a light confining layer 502b formed on the surface of the light confining layer 502 a.

When necessary, a gas-barrier layer may be formed on any one of thecomponent layers of the protective sheet, preferably, an inner layer.When a layer other than the base film, such as the light confininglayer, is the outermost layer, a protective layer may be formed on thesurface of the outermost layer by a film lamination process or resincoating process.

As mentioned above, the protective sheet thus formed is excellent instrength, heat resistance, weather resistance, transparency and gasimpermeability, and is capable of making incident light fall repeatedlyon the solar cells and of improving power generating efficiency.

The protective sheet and a photovoltaic layer provided with solar cellscan be laminated by sandwiching a resin film for forming an adhesivelayer between the protective sheet and the front surface of thephotovoltaic layer and laminating those component layers by a laminationprocess, in which those component layers are are bonded together by hotpressing.

A protective sheet in accordance with the present invention for a solarbattery module is intended to be used as a front protective sheet to bebonded to the front surface of a photovoltaic layer 507 provided withsolar cells. The protective sheet is a laminated film comprising a basefilm, an adhesive layer for bonding the protective sheet to aphotovoltaic layer provided with solar cells, and a light confininglayer or the protective sheet is a laminated film comprising a pluralityof layers including a base film, an adhesive layer for bonding theprotective sheet to a photovoltaic layer provided with solar cells, anda light confining layer. FIGS. 36(a) to 36(e) show protective sheets inaccordance with the present invention by way of example.

FIGS. 36(a) to 36(e) are typical sectional views of protective sheets(protective films) in accordance with the present invention for solarbattery modules. The protective sheet (protective film) shown in FIG.36(a) comprises a base film (weather-resistant sheet) 501, a lightconfining layer 502 a formed on the outer surface of the base film 501,i.e. a surface on the light receiving side of the base film 501, and anadhesive layer 503 for bonding the protective sheet to a photovoltaiclayer 507 provided with solar cells formed on the inner surface of thebase film 501, i.e., a surface to be bonded to the photovoltaic layer507.

The protective sheet shown in FIG. 36(b) comprises a base film(weather-resistant sheet) 501, a light confining layer 502 a formed onthe inner surface of the base film 501, i.e., a surface to be bonded toa photovoltaic layer 507 provided with solar cells, and an adhesivelayer 503 formed on the light confining layer 502 a.

The protective sheet shown in FIG. 36(c) comprises a base film 501 as anoutermost layer, an adhesive layer 503 formed on the inner surface ofthe base film 501, and a light confining layer 502 a formed on theadhesive layer 503. The light confining layer 502 a must be formed sothat the periphery thereof lies inside the periphery of the adhesivelayer 503 and a peripheral portion of the adhesive layer 503 is exposedto enable the adhesive layer 503 to exercise its bonding function.

The protective sheets shown in FIG. 36(d) comprises a base film 501, alight confining layer 502 a formed on the outer surface of the base film501, a light confining layer 502 b formed on the inner surface of thebase film 501, and an adhesive layer 503 formed on the light confininglayer 502b.

The protective sheets shown in FIG. 36(e) comprises a base film 501, alight confining layer 502 a formed on the inner surface of the base film501, a light confining layer 502 b formed on the surface of the lightconfining layer 502 a, and an adhesive layer 503 formed on the lightconfining layer 502 b.

When necessary, a gas-barrier layer may be formed on any one of thecomponent layers of the protective sheet, preferably, an inner layer.When a layer other than the base film, such as the light confininglayer, is the outermost layer, a protective layer may be formed on thesurface of the outermost layer by a film lamination process or resincoating process.

As mentioned above, the protective sheet thus formed is excellent instrength, heat resistance, weather resistance, transparency and gasimpermeability. Since the protective sheet is provided beforehand withthe adhesive layer for bonding the protective sheet to a photovoltaiclayer provided with solar cells, the adhesive layer can be formed in thelest necessary thickness, and the process for fabricating a solarbattery module is simplified. The protective sheet is capable of makinglight incident on the solar battery module fall repeatedly on the solarcells and of improving power generating efficiency.

FIGS. 37(a) and 37(b) are typical sectional views of light confininglayers for protective sheets in accordance with the present inventionfor solar battery modules. These light confining layers are the same asthose previously described with reference to FIGS. 37(a) and 37(b) andhence the description thereof will be omitted to avoid duplication.

FIG. 38(a) is a plan view of an irregular structure of assistance inexplaining the irregular structures of the light confining layers shownin FIGS. 37(a) and 37(b), FIG. 38(b) is a sectional view taken onlineA—A in FIG. 38(a) and FIG. 38(c) is a perspective view of the irregularstructure shown in FIG. 38(a).

As shown in FIG. 38(c), the light confining layer 502 has a corrugatedirregular structure formed by arranging ridges having a triangular crosssection. Preferably, the apex angle θ of the triangular cross section ofthe ridges is about 90°. An optimum apex angle of the triangular crosssection is 90° and a preferable height of the triangular cross sectionis in the range of 0.1 nm to 500 μm.

FIGS. 39(a) is a plan view of another light confining layer 502, FIG.39(b) is a sectional view taken on line A—A in FIG. 39(a), and FIG. 39(9c) is a perspective view of the light confining layer 502.

As obvious from FIG. 39(c), the light confining layer 502 shown in FIGS.39(a) to 39(c) has an irregular structure formed regularly arrangingpyramidal projections. Preferably, the apex angle θ of the triangularcross section of the pyramidal projections is about 90°. An optimum apexangle θ of the triangular cross section of the pyramidal projection is90° and a preferable height of the pyramidal projections is in the rangeof 0.1 nm to 500 μm.

FIG. 40 is a typical sectional view of a solar battery module 500provided with a protective film in accordance with the presentinvention.

As shown in FIG. 40, the solar battery module 500 is a laminatedstructure comprising a base film 501 as a front surface protectivesheet, a light confining layer 502, an adhesive layer 503, aphotovoltaic layer 507 provided with solar cells, and a substrate 508superposed in that order. The solar battery module may be fabricated,for example, by forming the photovoltaic layer 507 provided with solarcells on the substrate 508, superposing a protective sheet 510 formed bysuperposing and laminating the the base film 501, the light confininglayer 502 and the adhesive layer 503 in that order on the substrate 508provided with the photovoltaic layer 507, and bonding together theprotective sheet 510 and the substrate 508 provided with thephotovoltaic layer 507 by hot pressing.

When necessary, a gas-barrier layer may be formed on any one of thecomponent layers of the protective sheet 510. When necessary, a backsurface protective sheet similar to the protective sheet 510 may bebonded to the back surface, i.e., the outer surface, of the substrate508.

Since the front surface of the photovoltaic layer provided with solarcells is covered with the protective sheet excellent in strength, heatresistance, weather resistance, transparency and gas impermeability andcapable of making light incident on the solar battery module fallrepeatedly on the solar cells, the solar battery module is excellent inlong-term reliability, is capable of effectively using incident lightfallen on the solar cells and has excellent power generating ability.

EXAMPLES

Examples and a comparative example will be described below.

Example 1

A 75 μm thick ETFE film was used as a base film. A light confining layerhaving a corrugated irregular structure comprising ridges having atriangular cross section as shown in FIG. 38 was formed of anultraviolet curable acrylic resin on one of the surfaces of the 75 μmthick ETFE film. The triangular cross section was 8 μm in height and 60°in apex angle. A 80 nm thick textured layer of ZnO was deposited on thelight confining layer by a CVD process. A 70 nm thick deposited SiO_(x)film as a gas-barrier layer was formed on the textured layer by a CVDprocess to complete a protective sheet in Example 1 for a solar batterymodule.

Example 2

A protective sheet in Example 2 for a solar battery module of the samecomponents as those of Example 1 was fabricated by the same processes asin Example 1, except that the protective sheet in Example 2 was providedwith a light confining layer having a corrugated irregular structurecomprising ridges of a triangular cross section of 8 tun in height and90° in apex angle.

Example 3

A protective sheet in Example 3 for a solar battery module of the samecomponents as those of Example 1 was fabricated by the same processes asin Example 1, except that the protective sheet in Example 3 was providedwith a light confining layer having a corrugated irregular structurecomprising ridges of a triangular cross section of 8 μm in height and120° in apex angle.

Example 4

A protective sheet in Example 2 for a solar battery module of the samecomponents as those of Example 1 was fabricated by the same processes asin Example 1, except that the protective sheet in Example 4 was providedwith a light confining layer having an irregular structure comprisingpyramidal projections of a triangular cross section of 8 μm in heightand 60° in apex angle as shown in FIG. 39.

Example 5

A protective sheet in Example 5 for a solar battery module of the samecomponents as those of Example 4 was fabricated by the same processes asin Example 4, except that the protective sheet in Example 5 was providedwith a light confining layer having an irregular structure comprisingpyramidal projections of a triangular cross section of 8 μm in heightand 90° in apex angle.

Example 6

A protective sheet in Example 6 for a solar battery module of the samecomponents as those of Example 4 was fabricated by the same processes asin Example 4, except that the protective sheet in Example 6 was providedwith a light confining layer having an irregular structure comprisingpyramidal projections of a triangular cross section of 8 μm in heightand 120° in apex angle.

COMPARATIVE EXAMPLE 1

A protective sheet in Comparative example 1 for a solar battery moduleof the same components as those of Example 1 was fabricated, except thatthe protective sheet in Comparative example 1 was provided with a 8 μmthick flat ultraviolet curable acrylic resin film instead of the lightconfining layer.

Tests and Test Results

Solar battery modules in Examples 1 to 6 and Comparative 10 example 1were fabricated by bonding the protective sheets in Examples 1 to 6 andComparative example 1 by hot pressing to photovoltaic layers,respectively. Each photovoltaic layer was provided with amorphoussilicon solar cells formed on a glass substrate provided with adeposited Ag film as a reflecting layer.

Short-circuit currents J_(sc) (mA/cm²) in the solar battery modules inExamples 1 to 6 and Comparative example 1 were measured. Percentshort-circuit current increase based on the short-circuit current in thesolar battery moducle in Comparative example 1 was calculated. Measuredand calculated data are shown in Table 8-1.

TABLE 8-1 Test Result Short- Short-circuit circuit current IrregularApex Current improvement structure angle (J_(sc)(mA/cm²) ratio (%)Example 1 Corrugated 60° 30.5 4.8 Example 2 Corrugated 90° 31.1 6.9Example 3 Corrugated 120°  29.6 1.7 Example 4 Pyramidal 60° 30.8 5.8Example 5 Pyramidal 90° 31.2 7.2 Example 6 Pyramidal 120°  29.3 0.7Comparative Flat — 29.1 0 Example 1

As obvious from Table 8-1, the short-circuit currents in the solarbattery modules in Examples 1 to 6 employing the protective films inExamples 1 to 6 as their front surface protective sheets, respectively,are higher than that in the solar battery module in Comparative example1 employing the protective sheets in Comparative example 1, which provesthe effect of the light confining layer in increasing short-circuitcurrent.

The short-circuit current in the solar battery module in Example 5employing the protective sheet provided with the light confining layerhaving the irregular structure formed of the ultraviolet curable resinand comprising the pyramidal projections of a triangular cross sectionof 8 μm in height and 90° in apex angle is the highest and best amongthose in the solar battery modules in Examples 1 to 6.

As apparent from the foregoing description, the protective sheetaccording to the present invention for a solar battery module isexcellent in strength, heat resistance, weather resistance, transparencyand gas impermeability, and is capable of making light incident on thesolar battery module fall repeatedly on the solar cells to increaseshort-circuit current and power generating efficiency.

The adhesive layer for bonding the protective sheet to the photovoltaiclayer provided with solar cells can be formed beforehand on the innersurface of the protective sheet. Therefore, the adhesive layer can beformed in the least necessary thickness and the process for fabricatingthe solar battery module by bonding together the protective sheet andthe phpotvoltaic layer provided with solar cells can be simplified. Theprotective sheet makes light incident on the solar battery module fallrepeatedly on the solar cells and thereby increases power generatingefficiency.

The solar battery module employing the protective sheet as its frontsurface protective sheet or its back surface protective sheet isexcellent in long-term reliability and is capable of generating power ata high power generating efficiency and of being produced at highproductivity.

The materials mentioned in the description of the first to the seventhembodiment are applicable to the eighth embodiment.

What is claimed is:
 1. A protective sheet for a solar battery module,formed by superposing a pair of laminated structures each comprising aweather-resistant sheet and a deposited inorganic oxide thin film,wherein each of the laminated structures has a coating film of acomposite material comprising a condensation polymer produced throughthe hydrolysis of a silicon compound, formed on the deposited inorganicoxide thin film.
 2. A protective sheet for a solar battery module,formed by superposing a pair of laminated structures each comprising acyclic polyolefin weather-resistant sheet and a deposited inorganicoxide thin film.
 3. The protective sheet for a solar battery module,according to claim 2, wherein the pair of laminated structures arebonded together with an adhesive layer, an extruded adhesive resin layeror a resin sheet.
 4. The protective sheet for a solar battery module,according to claim 2, wherein the cyclic polyolefin sheet has a visibleradiation transmittance of 90% or above.
 5. The protective sheet for asolar battery module, according to claim 2, wherein the cyclicpolyolefin sheet contains an ultraviolet absorber and/or an oxidationinhibitor.
 6. The protective sheet for a solar battery module, accordingto claim 2, wherein the deposited inorganic oxide thin film is asingle-layer inorganic oxide thin film, a multilayer film consisting ofat least two inorganic oxide thin films or a composite film consistingof at least two deposited thin films of inorganic oxides different fromeach other.
 7. The protective sheet for a solar battery module,according to claim 3, wherein the adhesive layer, the extruded adhesiveresin layer or the resin sheet contains an ultraviolet absorber and/oran oxidation inhibitor.
 8. A solar battery module comprising: aphotovoltaic layer provided with solar cells; a pair of filler layerscontiguous respectively with opposite surfaces of the photovoltaic layerprovided with solar cells; and a pair of protective sheets contiguousrespectively with the pair of filler layers; wherein, at least one ofthe pair of protective sheets comprises a pair of superposed laminatedstructures each comprising a cyclic polyolefin weather-resistant sheetand a deposited inorganic oxide thin film.
 9. A solar battery modulecomprising: a photovoltaic layer provided with solar cells; a pair offiller layers contiguous respectively with opposite surfaces of thephotovoltaic layer provided with solar cells; and a pair of protectivesheets contiguous respectively with the pair of filler layers; wherein,at least one of the pair of protective sheets comprises a pair ofsuperposed laminated structures each comprising a weather-resistantsheet and a deposited inorganic oxide thin film, wherein each laminatedstructure has a coating film formed of a composite material comprising acondensed polymer produced through the hydrolysis of a silicon compoundon the deposited inorganic oxide thin film.